Fix precedence problem by replacing or with ||

Since Perl 5.22, it warns of possible precedence problem it cases
like : return $value or die('Sad');
return $value is tested, not $value. It can be fixed by either using
|| or by using () around the test.
The problem was already there in earlier versions of Perl but no
waring was issued.

...to match header, and ZMap expectations.

Fixes RT 444665.

This reverts commit 82c485e5.

...and merge in Z:ZMap::Core.