Converted Makefile.PL to use CPAN Meta Spec
Converted Makefile.PL to use CPAN Meta Spec

- Created %meta_merge which follows v2 of meta-spec
- Renamed %pre_reqs to $PREREQ_PM in Makefile.PL, which is what's used
  in most other Gtk2-Perl modules

cpanxaoc/perl-GStreamer,cpanxaoc/perl-GStreamer,GNOME/perl-GStreamer,GNOME/perl-GStreamer