System 56 released to users

[Moon at MIT-AI (David A. Moon)]

System 56 is now ready for general release.  Currently it is the installed
system on a couple of machines; it should get distributed more widely
in the next couple of days.

Most of the changes in this system are internal incompatible changes which
should not affect users.  These changes are in the way regions work, in the
editor, and in the window system.  A few notes:

This system will not run with microcode younger than 720, and that microcode
will not run with older systems.  When using the CC debugger on this system,
load the latest LISPM;QCOM and LCADR;QF into the debugger machine if it is
running an older system.

Any file that contains a COMPILE-FLAVOR-METHODS that creates a combined method
for the :EXPOSE or :DEEXPOSE messages, that defines a blinker, or that uses
the TV:PREPARE-SHEET macro will need to be recompiled for the new system, and
thereafter will not run in the old system.  Note that the TV:SHEET-FORCE-ACCESS
macro generates a TV:PREPARE-SHEET.

SETUP-KEYBOARD-DISPATCH-TABLE has been flushed.  This is mentioned because it is
in the manual.  It has been a year or more since it was useful for anything.

Documentation on the new "system" facility (which replaces pkg-load)
may be found in the file AI:LMMAN;MAKSYS.  This facility was introduced in system 55.

A new function VALUES-LIST, which is to VALUES as RETURN-LIST is to RETURN.

The ABORT key has been changed somewhat, as announced in a previous message.
Control-Z is still synonymous with ABORT in some programs.  If you have
opinions about whether or not this use of control-Z should be flushed, please
mail them in to BUG-LISPM.