Avoid stack scanning: unportable and undefined behavior, frequently breaks
with compiler updates.

Index: inc/avoffset.mk
--- inc/avoffset.mk.orig
+++ inc/avoffset.mk
@@ -8,7 +8,7 @@ include		$(SRCROOT)/$(RULESDIR)/rules.top
 INSDIR=		include/schily/$(OARCH)
 TARGET=		avoffset.h
 TARGETC=	avoffset
-CPPOPTS +=	-DUSE_SCANSTACK
+CPPOPTS +=	-DNO_SCANSTACK
 CPPOPTS +=	-D__OPRINTF__
 CFILES=		avoffset.c
 
