Remove frog from the repository.

frog/frogc.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#import('lang.dart', prefix: 'lang');
-#import('frog_leg.dart', prefix: 'leg');
-#import('minfrogc.dart', prefix: 'minfrogc');
-
-void main() {
-  lang.legCompile = leg.compile;
-  try {
-    minfrogc.main();
-  } catch (var exception, var trace) {
-    try {
-      print('Internal error: $exception');
-    } catch (var ignored) {
-      print('Internal error: error while printing exception');
-    }
-    try {
-      print(trace);
-    } finally {
-      exit(253);
-    }
-  }
-}