SETF

[JONL at MIT-MC (Jon L White)]

Unfortunately, the currentf SETF expander turns (SETF (CAR L) X)
into (PROGN (RPLACA L X) X), which isn't what the built in version does
-- it acts as if the expansion should be (RPLACA L X).  This difference
in return value makes it impossible to use the value of SETF.  Any
preferences for what the "return value" of SETF should be?