Container: Document several rarely used virtual functions

* gtk/src/container.hg: Add documentation for the following functions:
child_type(), forall(), composite_child(), [get|set]_child_property(). The
documentation comes from the C docs.

Bug #670206.
Container: Slight improvements to the vfunc documentation.

* gtk/src/container.hg:
Slight rewrite of documentation
Application: run(): Do not show the window until activation.

* gtk/src/application.[hg|ccg]: run(window): Only show the window in
an activate signal handler, to fix a crash caused by the application not
being registered when the GtkApplicationWindow tries to realize itself.
gen_scripts: Do not require a change to the PATH environment variable.

	* tools/gen_scripts/gdk_generate_docs.sh:
	* tools/gen_scripts/gdk_generate_enums.sh:
	* tools/gen_scripts/gdk_generate_methods.sh:
	* tools/gen_scripts/gtk_generate_docs.sh:
	* tools/gen_scripts/gtk_generate_enums.sh:
	* tools/gen_scripts/gtk_generate_methods.sh: Remove the need to change
	the PATH as I did in the glibmm gen_scripts.
Add some extra .defs entries needed for documentation.

	* gdk/src/gdk_extra_objects.defs:
	* gtk/src/gtk_extra_objects.defs: Add definitions needed by
	the documentation generator.
Add an extra .defs entry needed for documentation.

* gdk/src/gdk_extra_objects.defs: Add GdkOffscreenWindow.
AppChooserDialog: Fix property name in constructors.

* gtk/src/appchooserdialog.ccg: Change incorrect property name "file" to
the correct "gfile" in constructors.
Show get_type() in the API documentation.

* tools/m4/class_gtkobject.m4: Move the static get_type()
functions out of the ifdef so that doxygen can see them,
because they are sometimes needed, for instance when
implementing a custom container.
Bug #670212 (Mark Vender).
Application: Don't call add_window() before the application is registered.

* gtk/src/application.[hg|ccg]: Move the call to add_window() from
run(Window& window, int argc, char** argv) and run(Window& window) to
on_activate_show_main_window() and rename it to
on_activate_add_and_show_main_window(). Bug #681323.
Fix tiny docs typo.
3.4.1
Many small cleanup fixes

 * *.[hg|ccg]: Trim trailing whitespace. Remove useless Subversion tags. Remove
    unused code format tags. Remove excessive whitespace.
 * gtk/src/layout.ccg: Remove bogus copyrigth header.
Improve the use of _IGNORE.

* gtk/src/fontselection.hg:
* gtk/src/targetlist.hg:
* gtk/src/textview.hg: Correct an _IGNORE.
* gtk/src/iconview.hg: Remove _IGNORE(gtk_tree_view_get_tooltip_context).
* gtk/src/treemodelfilter.hg: Remove _IGNORE(gtk_tree_model_filter_new).
ApplicationWindow: Add class documentation.

        * gtk/src/applicationwindow.hg: Add class overview documentation
based on the GTK+ documentation.
3.4.2