ERRSET undoification in compiled code

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

the routine beginning at label "ERUNDO"  should be replaced with
ERUNDO:	SKIPN ERRTN
	JRST LSPRET
	SETZM TYOSW
	JRST ERUN0
as far as I can see, there is no need ever for ERUNDO to allow for
"errors" so come thru - this is only the ERSTP break-up upon successful
completion of an ERRSETted computation.