reflect: add FuncOf function

This also involves adding functions to typelinks along with a minor
change to ensure they are sorted correctly.

Change-Id: I054a79b6498a634cbccce17579f52c299733c2cf
Reviewed-on: https://go-review.googlesource.com/1996
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/reflect/export_test.go

@@ -44,3 +44,13 @@ func FuncLayout(t Type, rcvr Type) (frametype Type, argSize, retOffset uintptr,
 	ptrs = ft.kind&kindNoPointers == 0
 	return
 }
+
+func TypeLinks() []string {
+	var r []string
+	for _, m := range typelinks() {
+		for _, t := range m {
+			r = append(r, *t.string)
+		}
+	}
+	return r
+}