Use lowercase windows.h in includes to fix Windows cross compilation using mingw.

bench/BenchSysTimer_windows.h

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkBenchSysTimer_DEFINED
 #define SkBenchSysTimer_DEFINED
 
 //Time
 #define WIN32_LEAN_AND_MEAN 1
-#include <Windows.h>
+#include <windows.h>
 
 class BenchSysTimer {
 public:
     void startWall();
     void startCpu();
     double endCpu();
     double endWall();
 private:
     ULONGLONG fStartCpu;
     LARGE_INTEGER fStartWall;
 };
 
 #endif