* gdk/Selection.custom : add static fields for the primary,
secondary, and clipboard and clipboard selection Gdk.Atoms.
* glue/Makefile.am : add selection.c
* glue/selection.c : add glue to get the atoms.
* gtk/TextBuffer.custom : add a PasteClipboard overload for
pasting to the cursor location.
svn path=/trunk/gtk-sharp/; revision=16130
