The problem is that the SwInsText/SwDelText do not transfer the
"deleted-ness" of the text from one node to the other in the
SwTextFrame, so add a new hint that is sent after SwInsText & before
SwDelText to move the info that is in the extents vector.

Change-Id: I32d8dbe52a18556d8dc2c50a47246a6600fdb355