Added Gtk+ testing utilities.

Added Gtk+ testing utilities.

* gtk/gtktestutils.h, gtk/gtktestutils.c: added unit test utility functions.
for the most part, the functions herein involve navigating and interacting
with dialog elements programatically, to automate user interaction tests of
dialogs and widgets.

* gtk/gtk.h: include gtk/gtktestutils.h as public API.

* gtk/gtk.symbols: added gtk_test_* symbols.

* gtk/Makefile.am: include gtktestutils.h and gtktestutils.c into the build.
generate gtktypefuncs.c which contains a list of all _get_type functions in
Gtk+ and Gdk.

svn path=/trunk/; revision=19010