LP64: Make 9 patches architecture agnostic.

The Res_png_9patch struct had several pointer members
whose size differed between 32 and 64 bit platforms.

These members have been replaced by uint32_t offsets
to serialized data. The serialized form for 9patches
places a Res_png_9patch object at the beginning of
serialized data, followed by int32_t arrays of xDivs,
yDivs and colors.

Note that these offsets are not strictly required,
since they can be computed from the values of numXDivs,
numYDivs & numColors, however they are called in tight
loops so having them computed once is a beneficial.

This change also removed the unused patch_equals function
from aapt's Image.cpp.

Change-Id: I3b9ac8ae5c05510d41377cae4dff1c69b40c2531