powerpc64 / ppc64le support

[matthiasdiener]

WIP - not working yet and looking for feedback.

A few questions:

• Where are unwind-aarch64 etc. built? Edit: Nevermind, fixed in aa02cc7
• What is the purpose of the vmprof_eval function?

cc: @fijal @mattip

[matthiasdiener]

Current status: It works on powerpc64, but only for the Python callstack:

$ vmprofshow vmprof_cpuburn.dat tree
100.0%  <unknown code>  100.0%  <unknown>
100.0% |. test  100.0%  vmprof/test/cpuburn.py:36
100.0% |.|. burn  100.0%  vmprof/test/cpuburn.py:27
100.0% |.|.|. _iterate  100.0%  vmprof/test/cpuburn.py:20
 51.6% |.|.|.|. _next_rand  51.6%  vmprof/test/cpuburn.py:15

Not sure if this is a libbacktrace or libunwind issue.

[matthiasdiener]

It seems that native profiling is not available in ppc64le (no getcontext in libunwind libunwind/libunwind#33), so setting this as ready for review.

[matthiasdiener]

Gentle ping for @fijal @mattip for a review.

[mattip]

Thanks @matthiasdiener

[mattip]

Since we are running CI on travis, I think it would be nice to add a ppc64le job