Fix unit tests, and extend for other architectures

Fix unit tests, and extend for other architectures

On unpacking, reinstate any p_align values that packing reduced to
page size.  Ensures a round-trip pack and unpack is bit-equivalent
to the original input.
https://android-review.googlesource.com/#/c/148492/

Extend unit tests to include ia32, x64, and mips32.

Recreate test data for arm32 and arm64.  Generate new test data for
ia32, x64, and mips32.

Bug: http://b/20687795
Bug: http://b/18051137
Change-Id: Ifbca8e206ef447297ba4f19272b813702be27a35