add maskfilter to c api

include/c/sk_types.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // EXPERIMENTAL EXPERIMENTAL EXPERIMENTAL EXPERIMENTAL
 // DO NOT USE -- FOR INTERNAL TESTING ONLY
 
@@ skipping 62 matching lines @@
     float   right;
     float   bottom;
 } sk_rect_t;
 
 typedef struct {
     float   mat[9];
 } sk_matrix_t;
 
 typedef struct sk_canvas_t sk_canvas_t;
 typedef struct sk_image_t sk_image_t;
+typedef struct sk_maskfilter_t sk_maskfilter_t;
 typedef struct sk_paint_t sk_paint_t;
 typedef struct sk_picture_t sk_picture_t;
 typedef struct sk_picture_recorder_t sk_picture_recorder_t;
 typedef struct sk_path_t sk_path_t;
 typedef struct sk_shader_t sk_shader_t;
 typedef struct sk_surface_t sk_surface_t;
 
 //////////////////////////////////////////////////////////////////////////////////////////
 
 #ifdef __cplusplus
     class SkCanvas;
     void sk_test_capi(SkCanvas*);
 #endif
 
 SK_C_PLUS_PLUS_END_GUARD
 
 #endif