Change input method behavior to act on key presses instead of key

Change input method behavior to act on key presses instead of key

* modules/input/gtkimcontextmultipress.c (vfunc_filter_keypress):
Change input method behavior to act on key presses instead of
key releases, matching normal text input behavior.  This change
alleviates the need to take special action for control keys not
handled by the input module itself.

svn path=/trunk/; revision=18169