Revert commit 049cf5ac
richedit: Avoid notifying parent window in improper state.

The commit was meant to fix a problem caused by ME_SendSelChange being
called in ME_SendSelChange, but moving the calls to ME_CommitUndo caused
a regression. So this patch reverts the previous commit, and my
following patch will instead fix the bug by moving the call to
ME_SendSelChange out of ME_CommitUndo.