EH:CURRENT-FRAME as unbound variable doesn't work

[MOON at SCRC-TENEX]

This problem is specific to the trans-trap handler.  The problem is that it
should be looking at the location on which the trap occurred in the erring
stack group, probably using some variant of symeval-in-stack-group
(cdr-in-stack-group!).  There are numerous other manifestations of the
problem.  I will try to do something about this, since probably no one
else will.