Add --noImplicitThis flag

It's basically another --noImplicitAny error, but one that would break
large amount of JavaScript-style code.

src/compiler/commandLineParser.ts

@@ -125,6 +125,10 @@ namespace ts {
             type: "boolean",
             description: Diagnostics.Raise_error_on_expressions_and_declarations_with_an_implied_any_type,
         },
+        {
+            name: "noImplicitThis",
+            type: "boolean",
+        },
         {
             name: "noLib",
             type: "boolean",