Complete the major version jump. Gtk# 3 and 2 are now both
installable within the same prefix.
* */glue/Makefile.am: Produce *sharpglue-3 gluelibs.
* *.custom, *.cs: pinvoke the new glue library.
* *-2.0.pc.in: Rename to *-3.0.pc.in.
svn path=/trunk/gtk-sharp/; revision=140941
