Add F# and GLSL samples. Add Forth and GLSL extension .fs.

Add heuristic to disambiguate between F#, Forth, and GLSL.

samples/F#/sample.fs

@@ -0,0 +1,15 @@
+module Sample
+
+open System
+
+type Foo =
+    {
+        Bar : string
+    }
+
+type Baz = interface end
+
+let Sample1(xs : int list) : string =
+    xs
+    |> List.map (fun x -> string x)
+    |> String.concat ","