[Uim] refactoring candidate window of gtk-im-uim

[yusuke at cherubim.icw.co.jp]

Hi,

> Now I separated candidate window related codes from gtk/gtk-im-uim.c to
> uim-cand-win-gtk.c. Following file is the patch against r1033:
Good job!
It seems working well here and the code seems more maintainable.
However, your patch uses g_ptr_array_remove_range() which is a glib2.4 function.

> Can I commit this patch?
Please commit after you fix g_ptr_array_remove_range() issue.