** erase-buffer should perhaps disregard read-only properties of text.
-** Make occur correctly handle matches that span more than one line,
- as well as overlapping matches.
-
** Fix the kill/yank treatment of invisible text. At the moment,
invisible text is placed in the kill-ring, so that the contents of
the ring may not correspond to the text as displayed to the user.
** Enhance scroll-bar to handle tall line (similar to line-move).
-** Make occur handle multi-line matches cleanly with context.
-
** In Custom buffers, put the option that turns a mode on or off first,
using a heuristic of some kind?