bug generating duplicate interface signatures

R=r
OCL=15119
CL=15119
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 11d8b56..b7019bc 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -195,8 +195,9 @@
 
 	uchar	undef;		// a diagnostic has been generated
 	uchar	export;		// marked as export
-	uchar	exported;	// has been exported
+	uchar	exported;	// exported
 	uchar	sym;		// huffman encoding in object file
+	uchar	local;		// created in this file
 
 	char*	opackage;	// original package name
 	char*	package;	// package name
@@ -429,6 +430,7 @@
 EXTERN	Dcl*	paramdcl;
 EXTERN	Dcl*	externdcl;
 EXTERN	Dcl*	exportlist;
+EXTERN	Dcl*	signatlist;
 EXTERN	int	dclcontext;	// PEXTERN/PAUTO
 EXTERN	int	importflag;
 EXTERN	int	inimportsys;