gc: var x, ok = m[y]

Fixes #384.

R=ken2
https://golang.org/cl/179061

src/cmd/gc/sinit.c

@@ -94,6 +94,12 @@ init1(Node *n, NodeList **out)
 				init1(l->n, out);
 			*out = list(*out, n->defn);
 			break;
+		
+		case OAS2MAPR:
+			for(l=n->defn->rlist; l; l=l->next)
+				init1(l->n, out);
+			*out = list(*out, n->defn);
+			break;
 		}
 	}
 	l = initlist;

test/fixedbugs/bug227.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 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.
+
+package main
+
+var (
+	nf int
+	x, y, z = f(), f(), f()
+	m = map[string]string{"a":"A"}
+	a, aok = m["a"]
+	b, bok = m["b"]
+)
+
+func look(s string) (string, bool) {
+	x, ok := m[s]
+	return x, ok
+}
+
+func f() int {
+	nf++
+	return nf
+}
+
+func main() {
+	if nf != 3 || x != 1 || y != 2 || z != 3 {
+		panic("nf=", nf, " x=", x, " y=", y)
+	}
+	if a != "A" || aok != true || b != "" || bok != false {
+		panic("a=", a, " aok=", aok, " b=", b, " bok=", bok)
+	}
+}