cmd/compile: avoid function literal name collision with "glob"

The compiler was treating all global function literals as occurring in a
function named "glob", which caused a symbol name collision when there
was an actual function named "glob".  Fixed by adding a period.

Fixes #16193.

Change-Id: I67792901a8ca04635ba41d172bfaee99944f594d
Reviewed-on: https://go-review.googlesource.com/24500Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/gc/closure.go

@@ -166,7 +166,7 @@ func closurename(n *Node) *Sym {
 	prefix := ""
 	if n.Func.Outerfunc == nil {
 		// Global closure.
-		outer = "glob"
+		outer = "glob."
 
 		prefix = "func"
 		closurename_closgen++

test/fixedbugs/issue16193.go

+// compile
+
+// Copyright 2016 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.
+
+// The compiler used the name "glob" as the function holding a global
+// function literal, colliding with an actual function named "glob".
+
+package main
+
+func glob() {
+	func() {
+	}()
+}
+
+var c1 = func() {
+}
+
+var c2 = func() {
+}
+
+func main() {
+	glob()
+	c1()
+	c2()
+}