Also, added api to allow an input method to internally handle
key press and release events in the GtkTextView and GtkEntry
cases.
This is simply a wrapper to the gtk_im_context_filter_keypress()
function, but It's added to not access the ->im_context
directly.
Based on a Christian Dywan patch
Fixes https://bugzilla.gnome.org/show_bug.cgi?id=163251
7692a427a6