attempt to fix SDK build.

missing cdefs.h include

Change-Id: Ic7dfdfe74976a459f166a7576b077965cd1fda6a
diff --git a/include/system/graphics.h b/include/system/graphics.h
index 77cd337..2c97daf 100644
--- a/include/system/graphics.h
+++ b/include/system/graphics.h
@@ -17,6 +17,8 @@
 #ifndef SYSTEM_CORE_INCLUDE_ANDROID_GRAPHICS_H
 #define SYSTEM_CORE_INCLUDE_ANDROID_GRAPHICS_H
 
+#include <cdefs.h>
+
 __BEGIN_DECLS
 
 /*