gdk-pixbuf needs its own include directory

[Jeff Johnson]

GTK+ 3.0 needs GDK 3.0, which relies on gdk-pixbuf 2.0. In the LSB
formulation, we stick this in /opt/lsb/include/gtk-2.0. But we now need to be
able to pull in gdk-pixbuf without pulling in the rest of GDK and GTK+ 2.0.

So, we're moving gdk pixbuf to /opt/lsb/include/gdk-pixbuf-2.0.

This should be a clean move, since we rely on pkgconfig files to pull in the
extra include directories, so a few tweaks to those directories should suffice.
 So we need to make these changes:

 - change include file path in database

 - regen build_env/headers to drop/add the proper headers

 - edit stub_libs/$VERSION/pkgconfig/*.pc to include the new directory for all
of them which add the gtk-2.0 directory