A PERL5LIB directory containing modules built for an other version of
perl could cause problems.

In order to make https work in LWP.

This avoids errors with missing libbz2.so.1.0 on some Linux
distributions.

'readlink -f' doesn't work on OSX.

This should fix a problem with esr31 when the browser gets killed for
trying to use the mprotect system call.