cmd/compile: move ODCLFUNC Node.Nname into Node.Func.Nname

$ sizeof -p cmd/compile/internal/gc Node
Node 168
$

Change-Id: I7decd950fe068c0f294c6c9bff07ef809c394429
Reviewed-on: https://go-review.googlesource.com/10534
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -123,6 +123,7 @@ type Func struct {
 	Top        int   // top context (Ecall, Eproc, etc)
 	Closure    *Node // OCLOSURE <-> ODCLFUNC
 	FCurfn     *Node
+	Nname      *Node
 
 	Inl     *NodeList // copy of the body for use in inlining
 	InlCost int32