Move SkTHash.h to include/private.

include/views/SkOSWindow_Win.h includes it.

To move SkTHash.h to include/private, SkChecksum.h needs to go there too.  To move SkChecksum.h to include/private, SkTLogic needs to go there too.

This adds a bunch of -Iinclude/private to tools.gyp I missed in the last CL.

No public API changes.
TBR=reed@google.com

BUG=skia:4126

Review URL: https://codereview.chromium.org/1260613006
diff --git a/include/gpu/GrBlend.h b/include/gpu/GrBlend.h
index c8b931d..52a0300 100644
--- a/include/gpu/GrBlend.h
+++ b/include/gpu/GrBlend.h
@@ -7,7 +7,7 @@
  */
 
 #include "GrTypes.h"
-#include "../../src/utils/SkTLogic.h"
+#include "../private/SkTLogic.h"
 
 #ifndef GrBlend_DEFINED
 #define GrBlend_DEFINED