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

While it doesn't matter on Windows, mingw on case-sensitive OSes uses all lower case filenames for platform include files. I found the problem in SkCondVar.h from Mozilla checkout of skia sources, but the patch contains a fix for the whole skia tree.

R=bungeman@google.com

Review URL: https://codereview.chromium.org/99173003

git-svn-id: http://skia.googlecode.com/svn/trunk@12461 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/utils/SkCondVar.h b/include/utils/SkCondVar.h
index 15f16e66..861a2ab 100644
--- a/include/utils/SkCondVar.h
+++ b/include/utils/SkCondVar.h
@@ -11,7 +11,7 @@
 #ifdef SK_USE_POSIX_THREADS
 #include <pthread.h>
 #elif defined(SK_BUILD_FOR_WIN32)
-#include <Windows.h>
+#include <windows.h>
 #endif
 
 /**