STRING bug

[RWK at MIT-MC (Robert W. Kerns)]

Well, JONL has just made n^n small changes to the source, so it's kinda hard
for me to figure out if he's changed anything relevant.

It is possible that you're causing it by clobbering a string.  This is one
problem the MACLISP STRING implementation has.

The internal symptoms are that STR/:NO.STRINGS is getting to be larger than
STR/:GCMARRAY.  I'm not sure why.  Just SETQing it down to 1- the size of
STR/:GCMARRAY doesn't make the problem go away, it gets upped the next time
a GC is run.  I suspect a fencepost, but I'm not sure where.