gtkfilechooserbutton: fix documentation typo

https://bugzilla.gnome.org/show_bug.cgi?id=702695
Improve doc of gtk_text_iter_forward_search()

It was not possible to know if the @limit was for @match_start or
@match_end. It was documented for backward_search(), but not for
forward_search().

https://bugzilla.gnome.org/show_bug.cgi?id=390048
quartz: update the keymap only if the input method changed

and not on each keystroke, which for some IMs apparently caused a full
update on each keystroke, not just a check for changes. Patch from
Takuro Ashie, bug #698183.
quartz: remove check for keymap changes from update_keymap()

The function is now only called when the keymap has actually
changed. bug #698183.
(cherry picked from commit e62709da2ee6619f26c8446b545418e5f1b9e151)