test rename overhaul: step 8 - language tests

tests/language/many_generic_instanceof_test.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.
 
 #library("ManyGenericInstanceofTest.dart");
-#source("GenericInstanceof.dart");
+#source("generic_instanceof.dart");
 
 class ManyGenericInstanceofTest {
   static testMain() {
     for (int i = 0; i < 5000; i++) {
       GenericInstanceof.testMain();
     }
   }
 }
 
 main() {
   ManyGenericInstanceofTest.testMain();
 }