No more global globs ("DIR").
Will no longer run into deep recusion problems.
Will now properly clean up when getting '-c', which it didn't do before
in all cases.

Support for long command line switches:

Usage:
    ./runtests.pl [-c] [-v] [<test files or directories> ...]
    ./runtests.pl -l        [<test files or directories> ...]
    ./runtests.pl -h

    -l|--list|--tests|--list-tests
            list available tests
    -c|--clean|--clear
            run tests and clean up in each directory
            visited (default is not to clean up)
    -v|--verbose
            be verbose
    -h|--help
            display this help text