runtime: cleanup after conversion to Go

Change-Id: I7c41cc6a5ab9fb3b0cc3812cf7e9776884658778
Reviewed-on: https://go-review.googlesource.com/4671
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/proc.go

@@ -32,7 +32,9 @@ func main() {
 		maxstacksize = 250000000
 	}
 
-	systemstack(newsysmon)
+	systemstack(func() {
+		newm(sysmon, nil)
+	})
 
 	// Lock the main goroutine onto this, the main OS thread,
 	// during initialization.  Most programs won't care, but a few