Ensure alignment of Res_png_9patch.

This doesn't alter the alignment of the data within the struct, but
enforces that this structure will be appropriately aligned when used.

The image_info struct has this struct preceded by a bool, which causes
odd alignment for the members of this struct.

Change-Id: Ia2ef5c81b2f961c0f61858a10a7821d82f600919

include/androidfw/ResourceTypes.h

@@ -112,7 +112,7 @@ struct __assertChar16Size {
  *
  * The PNG chunk type is "npTc".
  */
-struct Res_png_9patch
+struct alignas(uintptr_t) Res_png_9patch
 {
     Res_png_9patch() : wasDeserialized(false), xDivsOffset(0),
                        yDivsOffset(0), colorsOffset(0) { }