System 79 and 83 QFASL files now compatible.

[Richard M. Stallman <RMS at MIT-AI>]

Both system 79 and system 83 have been patched so that files compiled
in either one will load into the other and work; but you must use
microcode 862 with system 79 to be sure of success.

If a file compiled in system 79 is loaded into system 83,
some of system 83's speed advantage in flavors with methods in that file
will be forfeit.  Also, in the unlikely case that you load old
compiled DECLARE-FLAVOR-INSTANCE-VARIABLES functions for a flavor
but do not load any old compiled methods for that flavor, it will
not work automatically.  Contact me if you think this is happening to you.

If a file compiled in system 83 is loaded into system 79,
combined methods produced by COMPILE-FLAVOR-METHODS will be ignored.
This may make your program slower to start up than it used to be,
but will have no other effects.

It is therefore best to compile your files in system 83, so that
they will get the full speed advantage when run in that system.

It should be noted that system 83 has the same compatibility definitions
that system 79 has, for the functions DEFUN-METHOD and INSTANCE-VARIABLE-BOUNDP
needed in brand S systems.  So code that has been changed to work in those
systems will also work in system 83.  QFASL files are not compatible
between 79/83 and 204, however.

I would like to apologize for not mentioning the now eliminated
incompatibility of QFASL files in the system message for system 83.
Sometimes when I know something by heart, I forget that other people
don't know it.