major code speedups, bug fixes, behavior

major code speedups, bug fixes, behavior
   refinements, doc-string clarification and elaboration, etc.
   Prominent new features include:
  - Exposure changes and navigation are greatly accelerated.
  - More elaborate and clear doc-string for outline-mode,
    giving better guidance on use of the mode.
  - A new exposure-layout syntax, which accomodates outlines
    with multiple top-level topics.  (See `outline-expose' and
    `outline-new-exposure'.)
  - Automatic exposure and verfication-prompting on attempts to
    change text within concealed regions, before they are
    applied.  (Undo affecting concealed regions is only
    exposed, not verified, to facilitate smooth undo sequences.)
 - 'hot-spot' navigation implemented.  When the cursor is on a
    topic's bullet, regular-character keystrokes will be
    interepreted as if they were preceded by ^C, when
    appropriate, so users can navigate and adjust exposure,
    etc, with single-stroke commands.
  - Lucid emacs accomodated.