Re-arrange buildme.sh to reduce clutter

- re-use same procedures for all perl versions, where possible
- allow user to pass Perl 5.18 (or other) location
Put Font::FreeType at the end of the list. It's an optional module.
Need to update JSON::XS for 5.18 compatibility
Add updated JSON::XS and DBI modules for Perl 5.18 compatibility.
Merge branch 'public/feature/7.8_new_buildscript' into public/7.8