audioresample: add OpenPOWER ppc64 support

audioresample includes some custom assembly

There is growing interest in the OpenPOWER architecture.

IBM is currently offering bounties to developers who will port free software projects to OpenPOWER

Providing an implementation of the code for OpenPOWER ISA appears to be a good idea for a bounty

Alternatively, could the custom assembly be managed as part of liborc?

A bounty was offered for similar work in ffmpeg libswscale and a developer has provided a solution for that