entrycompletion: set the GtkWindow as attached to the GtkEntry

This way themes can easily select that window to apply custom styles.

https://bugzilla.gnome.org/show_bug.cgi?id=708414
a11y: don't shutdown accessibility, so the atk bridge is always valid

This will fix issues in applications that for some reason make
several and not nested calls to gtk_main() during their lifetime,
effectively initializing a11y when the first, top most, main loop
is being run and shutting it down then that loop is quit.

https://bugzilla.gnome.org/show_bug.cgi?id=708024

https://bugzilla.gnome.org/show_bug.cgi?id=684076
Add a needs-attention child property to GtkStack

The child property is watched by the StackSwicther which in turns sets a
needs-attention css class on the corresponding button, so that the theme
can for instance show a throbbing animation if one of the hidden pages
needs the user attention.

https://bugzilla.gnome.org/show_bug.cgi?id=707153
GtkAboutDialog: prevent unintended visibility

Some of the labels were not marked as no-show-all. But the
code clearly tries to manage their visibility, so gtk_widget_show_all()
should not affect them.

https://bugzilla.gnome.org/show_bug.cgi?id=681484
GtkStack: Add more transition types

This adds new 'over' and 'under' transitions which work by moving
the new page over the previous one, or moving the previous page off
to reveal the new one. We also add an over/under combination that
is going to be used in GtkAboutDialog.

https://bugzilla.gnome.org/show_bug.cgi?id=707187
Test new transition types

We should make teststack pick up new transitions automatically.
For now, we have to add them manually.

https://bugzilla.gnome.org/show_bug.cgi?id=707187
Use a stack in GtkAboutDialog

This lets us slide the credits and license sections up and down,
instead of just popping them into existence abruptly.
Fixups to GtkStack

The GtkStack and GtkStackSwitcher code did not really
follow GTK+ conventions for includes. Fix that, and also
fix up a case of gpointer vs gpointer* confusion
in gtkstack.c.
Update Demos Visual Studio Projects

Improve optimization, by re-enabling WholeProgramOptimization but changing
the linker optimization to not drop items that are not referenced in code
(such as compiled gresource sources that are not directly referenced in
code, as they are still needed for the demos to run properly).