Added Paned and Aspect Frame tutorials.  Originally written
by Owen Taylor and posted to the gtk-list, but never made the
final cut.

Also, replaced one gtk_exit with a gtk_main_quit.  It should have
been done for all the code examples, so if you want to ignore that 
part of the patch, that's fine.

Also, a missing > on the </tt> on Gale's mail addy.  One format error
on gtk_scrolled_window_set_policy, and what appears to be a vi barf
in the scrolled window example (no idea what happened there)

Mark Crichton
crichton@expert.cc.purdue.edu