[opus] [Opus] [Patch]01-Add ARM5E macros

[Timothy B. Terriberry]

Peter Robinson wrote:
> Is this run time fast path detected or compile time tested? For
> generic distros like Fedora the later would be preferable because the
> HW it's compiled on is unlikely to be the same as it's running on.

For these optimizations, it's tested at compile time. These are tiny 
macros spread widely throughout the codebase, so runtime testing is 
infeasible.

As we move to more targeted optimization of specific functions, we will 
include runtime CPU detection, just as we have in other codecs.

> ARMv7 and NEON optimisations would be cool too.

Patches welcome, of course :).