(adjust_markers_for_insert):

(adjust_markers_for_insert):
New args COMBINED_AFTER_BYTES, COMBINED_BEFORE_BYTES.  Calls changed.
(insert_1): Call insert_1_both.
(count_combining_before): New function.
(count_combining_after): New function.
(insert_1_both, insert_from_string_1): Handle bytes that combine
with chars adjacent to the inserted text.
(insert_from_buffer_1, replace_range): Likewise.
(adjust_after_replace): New args COMBINED_BEFORE_BYTES, COMBINED_AFTER_BYTES.