argument, which specifies the value to return to the catch, or the
data to give to the condition handler. Renamed to
unwind_to_catch, to reflect new role.
(Fsignal, Fthrow): Removed code to set catch tag value and do the
long-jump; this is taken care of by unwind_to_catch.
about setting h.poll_suppress_count; it's guaranteed to be the
same as c.poll_suppress_count.
(internal_condition_case): Don't worry about
h.poll_suppress_count.
(Fsignal): Use h->tag->poll_suppress_count instead of
h->poll_suppress_count.
* eval.c (Fsignal): It's okay for the debugger to return to the
caller if the caller was signalling a quit.
* eval.c (unbind_catch): Restore the polling suppression count
here, instead of in Fsignal and Fthrow.
(Fthrow, Fsignal): Don't restore the polling suppression count here.
* eval.c (struct catchtag): More documentation.
* eval.c (entering_debugger): Variable renamed
when_entered_debugger, and is now a timestamp based on
num_nonmacro_input_chars.
(init_eval): Initialize when_entered_debugger, not
entering_debugger.
(call_debugger): Set when_entered_debugger to the current value of
num_nonmacro_input_chars.
(find_handler_clause): Don't call debugger unless
num_nonmacro_input_chars is greater than when_entered_debugger;
that way, we won't call the debugger unless the user has had a
chance to take control.
(Fbacktrace): Don't clear entering_debugger here.
