use correct lineno in nod even if yacc has looked ahead.
makes lineno correct for statements without semicolons.

R=ken
OCL=19454
CL=19454
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 54c47d0..c5e35a1 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -419,6 +419,7 @@
 EXTERN	Io	curio;
 EXTERN	Io	pushedio;
 EXTERN	int32	lineno;
+EXTERN	int32	prevlineno;
 EXTERN	char*	pathname;
 EXTERN	Hist*	hist;
 EXTERN	Hist*	ehist;