CJK Windows: Silence gtk_style_context_set_state() warnings

CJK Windows: Silence gtk_style_context_set_state() warnings

We need to update calls to gtk_style_context_set_state() in
gtkimcontextime.c, so that the state passed into that function would be in
line with what GtkStyleContext expects, due to updates in the CSS
machinery, as outlined in this link[1], which is based on information in
in Matthias' blog[2].

Doing so will silence the gtk_style_context_set_state() warnings, which is
emitted when a widget uses gtkimcontext on Windows with CJK IME, which will
in turn call gtkimcontextime.

[1]: http://feaneron.com/2016/01/04/quick-guide-to-port-an-app-for-gtk-3-20/
[2]: https://blogs.gnome.org/mclasen/2015/11/20/a-gtk-update/

https://bugzilla.gnome.org/show_bug.cgi?id=760314