TRACE  (TAA 1/31/77)
	Read MUDBUG;TRACE ORDER first.

	The new TRACE works by SETG'ing the given atom to its old gval,
chtyped to a new type:  one of TSUBR, TRSUBR, TRSUBR-ENTRY, and
TFUNCTION.  These types all have an APPLYTYPE of a function which
performs all tracing functions.  Therefore very little structure is
created when something is traced, and one can still examine/edit the
traced object directly.  The printtypes of TRSUBR and TRSUBR-ENTRY are
RSUBR and RSUBR-ENTRY, respectively, so they will continue to print
as if they are RSUBRs/RSUBR-ENTRYs.
	The information used by TRACE is stored in a vector which is PUT
on the new GVAL of whatever is traced under the TRACE indicator.  This
vector is of type TSTRUC!-ITRACE, and has a printtype which associates
option names with the current setting of each.  Thus <GET ,FOO TRACE>
FOO
IN-BREAK:  #FALSE ()
IN-PRINT:  T
OUT-PRINT:  T
OUT-BREAK:  #FALSE ()
VERBOSE:  #FALSE ()
The behavior of TRACE with respect to a particular function may be
modified by PUTting into this vector in the appropriate slot:  thus
<PUT <GET ,FOO TRACE> ,IN-BREAK T>  will cause FOO to break on entry. 
The GVALs of IN-BREAK, IN-PRINT, OUT-PRINT, OUT-BREAK, and VERBOSE are
offsets into the vector.
	Killing the vector (by saying <PUT ,FOO TRACE>) is NOT a
suitable method of untracing; it is, in fact, fatal.  The vector stores
the old value of the object traced, which is necessary to untrace it
since one cannot CHTYPE into SUBR's, RSUBR-ENTRY's, and so on.
	INDENTing is global over all traced functions.  In a sacrifice
of speed for tastefulness, this has been changed such that each call to
a TRACEd function binds INDENT as a special variable.  Thus,  or ERRET
will leave you in a winning state with respect to indenting. 
Unassigning INDENT (or setting it to <>) has the effect of turning off
indenting for all nested calls; once you pop out of whatever level you
were at when this occurred, indenting will be restored.  Thus, it is
very difficult to completely turn off indenting while you're running
programs.
	If an option is provided as something other than an atom or
false, the object provided will be EVAL'ed each time the function is
called; it is therefore possible to change the behavior dynamically.  Of
course, hacks such as <AND <PRINT .FOO> <>> are perfectly legal.  For
greater convenience, the LVAL of TRACE-ARGS is the TUPLE of arguments to
a traced function during its execution:  any predicate may examine this.
Similarly, the LVAL of TRACE-VAL is the value returned by the function,
which may be examined by predicates supplied for OUT-BREAK and
OUT-PRINT.  