Make sure files end with exactly one new line and police this in presubmit.

test/mjsunit/mul-exhaustive-part6.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 533 matching lines @@
 f(70368775634943, 2097153);
 f(140737450606593, 4194303);
 f(140737484161024, 4194304);
 f(140737517715455, 4194305);
 f(281474934767617, 8388607);
 f(281474968322048, 8388608);
 f(281475001876479, 8388609);
 f(562949903089665, 16777215);
 f(562949936644096, 16777216);
 f(562949970198527, 16777217);
-f(1125899839733761, 33554431);
+f(1125899839733761, 33554431);