Add new MouseCursor interface for setting the mouse cursor.

ppapi/native_client/src/shared/ppapi_proxy/ppb_mouse_cursor.srpc

+# Copyright (c) 2011 The Native Client Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# RPC methods used to implement PPB_MouseCursor calls from the plugin.
+
+{
+ 'name': 'PpbMouseCursorRpc',
+ 'rpcs': [
+          {'name': 'PPB_MouseCursor_SetCursor',
+           'inputs': [['instance', 'PP_Instance'],      # PP_Instance
+                      ['type', 'int32_t'],              # PP_MouseCursor_Type
+                      ['custom_image', 'PP_Resource'],  # PP_Resource
+                      ['hot_spot', 'char[]'],           # PP_Point
+                     ],
+           'outputs': [['success', 'int32_t'],          # PP_Bool
+                      ]
+          },
+         ]
+}