8l/prof.c: #if 0 is not accepted by the Plan 9 native toolchain.

The solution may be a bit of a sledgehammer, but it looks like
a temporary situation anyway.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4400042

src/cmd/8l/prof.c

@@ -36,7 +36,7 @@
 void
 doprof1(void)
 {
-#if 0	// TODO(rsc)
+#ifdef	NOTDEF  // TODO(rsc)
 	Sym *s;
 	int32 n;
 	Prog *p, *q;