embed: Check for state_flags_changed vfunc

In GTK+ 3.2, GtkWidgetClass.state_flags_changed did not have an
implementation inside GtkWidget, which means that running clutter-gtk
with an older GTK+ version will crash.

https://bugzilla.gnome.org/show_bug.cgi?id=681462
Release Clutter-GTK 1.2.2 (stable)
Post-release version bump to 1.2.2
remove gtk_clutter_texture_new() annotation

Constructor should not have any annotation.

https://bugzilla.gnome.org/show_bug.cgi?id=686697