fix input method bug in overwrite mode
fix input method bug in overwrite mode

when inputting a character using compose key, it would not overwrite, but
insert the character.

svn path=/trunk/KDE/kdelibs/kate/; revision=991349

jfmcarreira/kate,hlamer/kate,DickJ/kate,sandsmark/kate,hlamer/kate,cmacq2/kate,jfmcarreira/kate,hlamer/kate,DickJ/kate,sandsmark/kate,hlamer/kate,hlamer/kate,sandsmark/kate,sandsmark/kate,DickJ/kate,hlamer/kate,hlamer/kate,jfmcarreira/kate,hlamer/kate,hlamer/kate,DickJ/kate,cmacq2/kate,cmacq2/kate,hlamer/kate