better libcurl checking.

enables us to check features of libcurl on users system.
we're not currently doing this, but possibly needed in future.

src/libcurl.m4

+# LIBCURL_CHECK_CONFIG ([DEFAULT-ACTION], [MINIMUM-VERSION],
+#                       [ACTION-IF-YES], [ACTION-IF-NO])
+# ----------------------------------------------------------
+#      David Shaw <dshaw@jabberwocky.com>   Jan-23-2005
+#
+# Checks for libcurl.  DEFAULT-ACTION is the string yes or no to
+# specify whether to default to --with-libcurl or --without-libcurl.
+# If not supplied, DEFAULT-ACTION is yes.  MINIMUM-VERSION is the
+# minimum version of libcurl to accept.  Pass the version as a regular
+# version number like 7.10.1. If not supplied, any version is
+# accepted.  ACTION-IF-YES is a list of shell commands to run if
+# libcurl was successfully found and passed the various tests.
+# ACTION-IF-NO is a list of shell commands that are run otherwise.
+# Note that using --without-libcurl does run ACTION-IF-NO.
+#
+# This macro defines HAVE_LIBCURL if a working libcurl setup is found,
+# and sets @LIBCURL@ and @LIBCURL_CPPFLAGS@ to the necessary values.
+# Other useful defines are LIBCURL_FEATURE_xxx where xxx are the
+# various features supported by libcurl, and LIBCURL_PROTOCOL_yyy
+# where yyy are the various protocols supported by libcurl.  Both xxx
+# and yyy are capitalized.  See the list of AH_TEMPLATEs at the top of
+# the macro for the complete list of possible defines.  Shell
+# variables $libcurl_feature_xxx and $libcurl_protocol_yyy are also
+# defined to 'yes' for those features and protocols that were found.
+# Note that xxx and yyy keep the same capitalization as in the
+# curl-config list (e.g. it's "HTTP" and not "http").
+#
+# Users may override the detected values by doing something like:
+# LIBCURL="-lcurl" LIBCURL_CPPFLAGS="-I/usr/myinclude" ./configure
+#
+# For the sake of sanity, this macro assumes that any libcurl that is
+# found is after version 7.7.2, the first version that included the
+# curl-config script.  Note that it is very important for people
+# packaging binary versions of libcurl to include this script!
+# Without curl-config, we can only make educated guesses as to what
+# protocols are available.  Specifically, we assume that all of HTTP,
+# FTP, GOPHER, FILE, TELNET, LDAP, and DICT exist, and (if SSL exists)
+# HTTPS is present.  All of these protocols existed when libcurl was
+# first created in version 7, so this is a safe assumption.  If the
+# version is 7.11.0 or later, FTPS is assumed to be present as well.
+# FTPS existed before then, but was not yet fully standards compliant.
+
+AC_DEFUN([LIBCURL_CHECK_CONFIG],
+[
+  AH_TEMPLATE([LIBCURL_FEATURE_SSL],[Defined if libcurl supports SSL])
+  AH_TEMPLATE([LIBCURL_FEATURE_KRB4],[Defined if libcurl supports KRB4])
+  AH_TEMPLATE([LIBCURL_FEATURE_IPV6],[Defined if libcurl supports IPv6])
+  AH_TEMPLATE([LIBCURL_FEATURE_LIBZ],[Defined if libcurl supports libz])
+  AH_TEMPLATE([LIBCURL_FEATURE_ASYNCHDNS],[Defined if libcurl supports AsynchDNS])
+
+  AH_TEMPLATE([LIBCURL_PROTOCOL_HTTP],[Defined if libcurl supports HTTP])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_HTTPS],[Defined if libcurl supports HTTPS])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_FTP],[Defined if libcurl supports FTP])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_FTPS],[Defined if libcurl supports FTPS])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_GOPHER],[Defined if libcurl supports GOPHER])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_FILE],[Defined if libcurl supports FILE])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_TELNET],[Defined if libcurl supports TELNET])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_LDAP],[Defined if libcurl supports LDAP])
+  AH_TEMPLATE([LIBCURL_PROTOCOL_DICT],[Defined if libcurl supports DICT])
+
+  AC_ARG_WITH(libcurl,
+     AS_HELP_STRING([--with-libcurl=DIR],[look for the curl library in DIR]),
+     [_libcurl_with=$withval],[_libcurl_with=ifelse([$1],,[yes],[$1])])
+
+  if test "$_libcurl_with" != "no" ; then
+
+     AC_PROG_AWK
+
+     _libcurl_version_parse="eval $AWK '{split(\$NF,A,\".\"); X=256*256*A[[1]]+256*A[[2]]+A[[3]]; print X;}'"
+
+     _libcurl_try_link=yes
+
+     if test -d "$_libcurl_with" ; then
+        CPPFLAGS="${CPPFLAGS} -I$withval/include"
+        LDFLAGS="${LDFLAGS} -L$withval/lib"
+     fi
+
+     AC_PATH_PROG([_libcurl_config],[curl-config])
+
+     if test x$_libcurl_config != "x" ; then
+        AC_CACHE_CHECK([for the version of libcurl],
+	   [libcurl_cv_lib_curl_version],
+           [libcurl_cv_lib_curl_version=`$_libcurl_config --version | $AWK '{print $[]2}'`])
+
+	_libcurl_version=`echo $libcurl_cv_lib_curl_version | $_libcurl_version_parse`
+	_libcurl_wanted=`echo ifelse([$2],,[0],[$2]) | $_libcurl_version_parse`
+
+        if test $_libcurl_wanted -gt 0 ; then
+	   AC_CACHE_CHECK([for libcurl >= version $2],
+	      [libcurl_cv_lib_version_ok],
+              [
+   	      if test $_libcurl_version -ge $_libcurl_wanted ; then
+	         libcurl_cv_lib_version_ok=yes
+      	      else
+	         libcurl_cv_lib_version_ok=no
+  	      fi
+              ])
+        fi
+
+	if test $_libcurl_wanted -eq 0 || test x$libcurl_cv_lib_version_ok = xyes ; then
+           if test x"$LIBCURL_CPPFLAGS" = "x" ; then
+              LIBCURL_CPPFLAGS=`$_libcurl_config --cflags`
+           fi
+           if test x"$LIBCURL" = "x" ; then
+              LIBCURL=`$_libcurl_config --libs`
+           fi
+
+	   # All curl-config scripts support --feature
+	   _libcurl_features=`$_libcurl_config --feature`
+
+           # Is it modern enough to have --protocols? (7.12.4)
+	   if test $_libcurl_version -ge 461828 ; then
+              _libcurl_protocols=`$_libcurl_config --protocols`
+           fi
+	else
+           _libcurl_try_link=no
+	fi
+
+	unset _libcurl_wanted
+     fi
+
+     if test $_libcurl_try_link = yes ; then
+
+        # we didn't find curl-config, so let's see if the user-supplied
+        # link line (or failing that, "-lcurl") is enough.
+        LIBCURL=${LIBCURL-"-lcurl"}
+
+        AC_CACHE_CHECK([whether libcurl is usable],
+           [libcurl_cv_lib_curl_usable],
+           [
+           _libcurl_save_cppflags=$CPPFLAGS
+           CPPFLAGS="$CPPFLAGS $LIBCURL_CPPFLAGS"
+           _libcurl_save_ldflags=$LDFLAGS
+           LDFLAGS="$LDFLAGS $LIBCURL"
+
+           AC_LINK_IFELSE(AC_LANG_PROGRAM([#include <curl/curl.h>],[
+/* Try and use a few common options to force a failure if we are
+   missing symbols or can't link. */
+int x;
+curl_easy_setopt(NULL,CURLOPT_URL,NULL);
+x=CURL_ERROR_SIZE;
+x=CURLOPT_WRITEFUNCTION;
+x=CURLOPT_FILE;
+x=CURLOPT_ERRORBUFFER;
+x=CURLOPT_STDERR;
+x=CURLOPT_VERBOSE;
+]),libcurl_cv_lib_curl_usable=yes,libcurl_cv_lib_curl_usable=no)
+
+           CPPFLAGS=$_libcurl_save_cppflags
+           LDFLAGS=$_libcurl_save_ldflags
+           unset _libcurl_save_cppflags
+           unset _libcurl_save_ldflags
+           ])
+
+        if test $libcurl_cv_lib_curl_usable = yes ; then
+           AC_DEFINE(HAVE_LIBCURL,1,
+             [Define to 1 if you have a functional curl library.])
+           AC_SUBST(LIBCURL_CPPFLAGS)
+           AC_SUBST(LIBCURL)
+
+           for _libcurl_feature in $_libcurl_features ; do
+	      AC_DEFINE_UNQUOTED(AS_TR_CPP(libcurl_feature_$_libcurl_feature),[1])
+	      eval AS_TR_SH(libcurl_feature_$_libcurl_feature)=yes
+           done
+
+	   if test "x$_libcurl_protocols" = "x" ; then
+
+	      # We don't have --protocols, so just assume that all
+	      # protocols are available
+	      _libcurl_protocols="HTTP FTP GOPHER FILE TELNET LDAP DICT"
+
+	      if test x$libcurl_feature_SSL = xyes ; then
+	         _libcurl_protocols="$_libcurl_protocols HTTPS"
+
+		 # FTPS wasn't standards-compliant until version
+		 # 7.11.0
+		 if test $_libcurl_version -ge 461568; then
+		    _libcurl_protocols="$_libcurl_protocols FTPS"
+		 fi
+	      fi
+	   fi
+
+	   for _libcurl_protocol in $_libcurl_protocols ; do
+	      AC_DEFINE_UNQUOTED(AS_TR_CPP(libcurl_protocol_$_libcurl_protocol),[1])
+	      eval AS_TR_SH(libcurl_protocol_$_libcurl_protocol)=yes
+           done
+        fi
+     fi
+
+     unset _libcurl_try_link
+     unset _libcurl_version_parse
+     unset _libcurl_config
+     unset _libcurl_feature
+     unset _libcurl_features
+     unset _libcurl_protocol
+     unset _libcurl_protocols
+     unset _libcurl_version
+  fi
+
+  if test x$_libcurl_with = xno || test x$libcurl_cv_lib_curl_usable != xyes ; then
+     # This is the IF-NO path
+     ifelse([$4],,:,[$4])
+  else
+     # This is the IF-YES path
+     ifelse([$3],,:,[$3])
+  fi
+
+  unset _libcurl_with
+])dnl