Cut/copy/paste via the X clipboard.
Generalized extending selection using <Shift> to work with all types
of motion, not just arrow keys.
Don't change length of GtkEntry structure because of USE_XIM
-owt
Takashi Matsuda <matsu@arch.comp.kyutech.ac.jp>
TANAKA Shinya <shinya@race.u-tokyo.ac.jp>
See ChangeLog entries for further details.
Also some small fixes to event handling in gdk/gdk.c; sending
clear events in gtk/gtkselection.c and cut-and-paste in
gtk/gtkentry.c
