GDK_WINDOW_XID() instead of GDK_DRAWABLE_XID()
GDK_WINDOW_XDISPLAY() instead of GDK_DRAWABLE_XDISPLAY()

No need for the function. Macros exist to do the same thing.

It's not used anymore

Instead of lots of magic, we can go the usual way of requesting the
XDisplay of the window's display. So we do that.

Also moves the function implementations to gtkwindow-x11.c.

No point in setting the alignment to centre if we don't center it
within the cell itself.

Recent changes cause disposing menus to emit ::deactivate. So better
disconnect the deactivate handler first.

This allows to pre-select a custom item.

Even in case there are no installed applications for our content type.

When setting a GtkRange's upper and lower values to the same
value, the slider will not be drawn any more.

https://bugzilla.gnome.org/show_bug.cgi?id=549720

Thomas Wood pointed out that the original MxGtkLightSwitch widget upon
which I based the behaviour of GtkSwitch was not written by him; the
original authors are:

  Joshua Lock
  Robert Staudinger
  Jussi Kukkonen

My apologies to all of them.

Conflicts:
	docs/reference/gtk/gtk3-sections.txt
	gtk/gtk.symbols

Based on a patch by Matthias, add an "active-id" property for
GtkComboBox and add some convenience API for GtkComboBoxText.

Also, add a test case to gtk-demo.

ATK provides macros to the same effect as G_DEFINE_TYPE; using these
macros has the advantage of removing tons of duplicated code and
reducing the maintainership burden.

The widgets with inline accessibility implementation should switch to
these macros, and clean up the code.

https://bugzilla.gnome.org/show_bug.cgi?id=636060

ATK provides macros to the same effect as G_DEFINE_TYPE; using these
macros has the advantage of removing tons of duplicated code and
reducing the maintainership burden.

The widgets with inline accessibility implementation should switch to
these macros, and clean up the code.

https://bugzilla.gnome.org/show_bug.cgi?id=636060