Fix polyd trapping when running pic and grn during groff tool builds on

vax.  From OpenBSD:

Addressing mode work by Jim Uhl:
    - fix PC relative byte displacement in getaddr_byte
    - add support for word displacement to getaddr_byte

This allows certain libm inverse trig functions to work on systems
that lack a native polyd instruction.

sys/arch/vax/vax/unimpl_emul.S

@@ -1,4 +1,4 @@
-/*	$NetBSD: unimpl_emul.S,v 1.2 2002/02/24 01:04:27 matt Exp $	*/
+/*	$NetBSD: unimpl_emul.S,v 1.3 2007/04/17 22:47:50 mhitch Exp $	*/
 
 /*
  * Copyright (c) 2001 Brandon Creighton.  All rights reserved.
@@ -351,7 +351,7 @@ getaddr_byte:
 	.word	2f-0b		# 9 autoincr deferred (missing)
 	.word	7f-0b		# 10 byte disp 
 	.word	2f-0b		# 11 byte disp deferred (missing)
-	.word	2f-0b		# 12 word disp (missing)
+	.word	8f-0b		# 12 word disp
 	.word	2f-0b		# 13 word disp deferred (missing)
 	.word	1f-0b		# 14 long disp
 	.word	2f-0b		# 15 long disp deferred (missing)
@@ -382,15 +382,30 @@ getaddr_byte:
 7:	
 	extzv	$0, $4, (%r3), %r2	# get register 
 	incl	%r3
-	movl	%r3, S_PC
-	ashl	$2,%r2,%r2
-	addl2	%fp,%r2
-	movl	(%r2),%r5
-	movzbl	(%r3),%r4
-	movl	S_PC, %r3
+	movl	(%fp)[%r2],%r0		# Register contents
+	pushl	%r4
+	cvtbl	(%r3),%r4
+	addl2	%r4,%r0			# add displacement
+	movl	(%sp)+,%r4
+	cmpl	%r2,$15			# pc?
+	bneq	0f			# no, skip
+	addl2	$2,%r0			# compensate for displacement size
+0:	incl	%r3			# increase pc
+	brw	4f
+
+8:	
+	extzv	$0, $4, (%r3), %r2	# get register 
 	incl	%r3
-	addl3	%r4, %r5, %r0
-	brw		4f
+	movl	(%fp)[%r2],%r0		# Register contents
+	pushl	%r4
+	cvtwl	(%r3),%r4
+	addl2	%r4,%r0			# add displacement
+	movl	(%sp)+,%r4
+	cmpl	%r2,$15			# pc?
+	bneq	0f			# no, skip
+	addl2	$3,%r0			# compensate for displacement size
+0:	addl2	$2,%r3			# increase pc
+	brw	4f
 
 6:	extzv	$0,$4,(%r3),%r2	# Get reg number
 	incl	%r3