[opus] [PATCH] 02-Add CELT filter optimizations

[Timothy B. Terriberry]

Aurélien Zanelli wrote:
> Patch changes are:
> - Use MAC16_16 macros instead of (sum += a*b) and unroll a loop by 2. It
> increase performance when using optimized macros (ex: ARMv5E). A
> possible side effect of loop unroll is that i don't check for odd length
> here.
> - Add NEON version of FIR filter and autocorr
> - Add a section in autoconf in order to check NEON support

I split out the arch-independent changes and committed them as
<https://git.xiph.org/?p=opus.git;h=85ede2c6aa06;a=commitdiff>.