gc: iota outside const

Fixes #1662.

R=ken2
CC=golang-dev
https://golang.org/cl/4828045

src/cmd/gc/lex.c

@@ -218,6 +218,7 @@ main(int argc, char *argv[])
 		curio.nlsemi = 0;
 
 		block = 1;
+		iota = -1000000;
 
 		yyparse();
 		if(nsyntaxerrors != 0)

test/fixedbugs/bug362.go

+// errchk $G $D/$F.go
+
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// issue 1662
+// iota inside var
+
+package main
+
+var (
+	a = iota  // ERROR "undefined: iota"
+	b = iota  // ERROR "undefined: iota"
+	c = iota  // ERROR "undefined: iota"
+)