success in removing recently added defvar

[<don...@is...>]

I notice in recent clisp-cvs Digests changes to bind -per-thread 
"non-global" special variables.
I've now removed the defvar I had to add because such vars had not
been bound per thread, and just want to report that the code seems
to be working.

I guess this can now be removed from the doc for make-thread:
  Note that symbols should be global SPECIAL variables (e.g.,
  declared as such by DEFVAR, DEFPARAMETER, etc).
BTW, I assume that a variable in this list is bound as a special even
if it was never declared as such, similar to progv, right?

I also noticed in the same patch changes to
MT:*DEFAULT-SPECIAL-BINDINGS* which I thought were strange.
Why is gensym counter in that list?
This is going to make debugging more difficult.
I suggest instead that gensym should use its own critical section.

I assumed that the initial thread is created with -per-thread bindings 
from MT:*DEFAULT-SPECIAL-BINDINGS* but experimentation suggests
otherwise. 
So I guess in that particular thread a plain setf can be used to
change the "global" values of variables.
This might be worth mentioning in the doc.

What do you think of trading
 (MT:SYMBOL-VALUE-THREAD symbol thread)
for
 (MT:GLOBAL-VALUE symbol)
and making SYMBOL-VALUE mean the -per-thread value if there is one?

My goal here is for code using SYMBOL-VALUE and originally written
for non threaded implementations to run in a new thread without
modification.  I think that this proposal corresponds better to the
normal meaning of symbol-value than the current implementation.