It turns out it is more convenient to have only pkgconfig files named
after the installed GStreamer API version (1.0) instead of using all
possible subsequent names from that (1.0, 1.2, 1.4). i.e. they conflict
altogether anyway, so align pkgconfig file names to that.
Fix the pluginsdir and includedir variables in the generated pkgconfig
(.pc) files. The location needs to be built with the PKG version in
mind instead of the API version.
While we are at it, also fix the PKG version for GStreamer >= 1.3.
https://bugzilla.gnome.org/show_bug.cgi?id=720820
[additional fixes for includedir and pkg requirements]
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>