cmd/api: more runtime fixes

This is getting a little annoying, but once the runtime structs are
being defined in Go, these will go away. So it's only a temporary cost.

TBR=bradfitz
CC=golang-codereviews
https://golang.org/cl/135940043

src/cmd/api/goapi.go

@@ -385,7 +385,7 @@ func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
 			" mcache struct{}; bucket struct{}; sudog struct{}; g struct{};" +
 			" hchan struct{}; chantype struct{}; waitq struct{};" +
 			" note struct{}; wincallbackcontext struct{};" +
-			" gobuf struct{}; funcval struct{};" +
+			" gobuf struct{}; funcval struct{}; _func struct{};" +
 			"); " +
 			"const ( cb_max = 2000 )"
 		f, err = parser.ParseFile(fset, filename, src, 0)