* now uses the short version for vendor and site paths: they are
supposed to be compatible for even version numbers. needs to rebuild
perl modules though.
* perl-5.18.1 doesn't exhibit cpan-related problems seen with 5.10.1
* adjusted @INC such that perl modules installed to ~/config
(or ~/config/non-packaged) are picked up by a perl installed
into /system, too
* drop public libperl.so and link perl using an rpath instead
* no longer link every module built by ExtUtils::MakeMaker against
libperl.so, as that isn't required for Haiku at all
* adjust ExtUtils::MakeMaker to not use -rpath when linking dynamic
perl modules that require other libraries
