Should improve performance on all platforms (from http://opus-codec.org) :

* x86 SSE, SSE2 and SSE4.1 intrinsics optimizations with run-time CPU detection contributed by Cisco Systems,
* MIPS intrinsics optimizations contributed by Imagination Technologies,
* ARM Neon optimizations contributed by Linaro and ARM

Tuleap: #407
Change-Id: I3dbd47a89abc7de99132843ff6b899b2b809ab47