This is a copy of a few libunwind headers from https://android.googlesource.com/platform/external/libunwind

We can't make the repo a git submodule because it contains a folder called 'aux' which
is reserved on Windows and would break on checkout there.

These files are unmodified from the originals and should preferably stay that
way to avoid merge hell.

Commit: 338c9755cfe3d009c3dfff7d108e2c3ddaa6f3bb (android-6.0.1_r24)