(adjust_markers_for_replace): Don't adjust a byte

(adjust_markers_for_replace): Don't adjust a byte
position if it is FROM.
(adjust_markers_for_combining): New function.
(combine_bytes): Call adjust_markers_for_combining instead of
adjust_markers_for_replace.
(adjust_after_replace): Record deletion of combining after bytes
with the correct position.  Don't add combining bytes to the args
given to adjust_point.  Handle correctly the case that there are
both before and after combining bytes.
(replace_range): Likewise.  Record the actual deletion after
recoding deletions of combining bytes.