Cleaning up {simple, twopass}_encoder examples.

Change-Id: Ide9c408f4cee7408741ef8c0ffac01645a5a67ca
diff --git a/tools_common.h b/tools_common.h
index 967b7a1..0f60c4c 100644
--- a/tools_common.h
+++ b/tools_common.h
@@ -129,6 +129,10 @@
 // of vpx_image_t support
 void vpx_img_write(const vpx_image_t *img, FILE *file);
 
+// TODO(dkovalev): move this function to vpx_image.{c, h}, so it will be part
+// of vpx_image_t support
+int vpx_img_read(vpx_image_t *img, FILE *file);
+
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif