do better bad-pointer testing

mach/mantra/int/deffile

@@ -74,7 +74,9 @@
 #endif
 #define  adroff move.b	(a3)+,(a5) ;	move.b	(a3)+,1(a5)
 #define	claimstack	tst.b	-1024(sp)
-#define	locptr	cmp.l	sp,a0 ;\
+#define	locptr	cmp.l	topstack,a0 ;\
+		bhi	7f ;\
+		cmp.l	sp,a0 ;\
 		bcc	6f  
 #define	heaptr	cmp.l	hp,a0 ;\
 		bhi	7f ;\

mach/mantra/int/mloop0

@@ -12,6 +12,7 @@
 	.define tblmax
 	.define ml
 	.define argc
+	.define topstack
 .sect .text
 .sect .rom
 .sect .data
@@ -22,6 +23,7 @@
 !---------------------------------------------------------------------------
 
 _m_a_i_n:
+		move.l	sp,topstack
 		tst.l	(sp)+
 		lea	retarea,a5		!a5 POINTS AT RETURN AREA
 		move.l	nd,-(sp)		!nd contains endbss
@@ -507,6 +509,7 @@ maxcount:  .space 4
 
 tblmax:	.space	4
 globmax: .space	4
+topstack: .space 4
 ml:	.space	4
 eb:	.space	4		!EXPLICITELY REQUIRED eb, filb, curproc IN
 filb:	.space	4		!THIS ORDER