gc: nits

R=ken2
CC=golang-dev
https://golang.org/cl/4572052

src/cmd/gc/pgen.c

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-#undef	EXTERN
-#define	EXTERN
 #include	"gg.h"
 #include	"opt.h"
 

src/cmd/gc/print.c

@@ -134,6 +134,10 @@ exprfmt(Fmt *f, Node *n, int prec)
 		fmtprint(f, "(node %O)", n->op);
 		break;
 
+	case OREGISTER:
+		fmtprint(f, "%R", n->val.u.reg);
+		break;
+
 	case OLITERAL:
 		if(n->sym != S) {
 			fmtprint(f, "%S", n->sym);