1a) Isolate Nindy-960 stuff into subsection of above, and expand it;
(2) Expand GDB-under-Emacs chapter;
(3) Minor cosmetics, including small free software blurb at front to
make RMS feel better about GPL moved to back.
document transmutation of add-file into sym-file and new meaning for
"load" (dynamic link/download, target-rel); document "info target" and
warn about similarity with "info targets"; document target strata rather
than stack; document "up-silently" and "down-silently"; add text about
when value history discarded.
gdb no longer prints the copyright and blurb if you specify a file
name to be debugged (just like Emacs). Add doc for Nindy-specific
command line flags for specifying target serial port and such.
Update copyright to 1991.
