[opus] arm64 support

[Martin Storsjö]

On Fri, 13 Jun 2014, Jean-Marc Valin wrote:

> On 26/03/14 07:11 AM, Vinay wrote:
>> I wanted to build opus along with PJSIP for iOS for the architecture
>> arm64. I wanted to know if opus supports arm64?
>
> I haven't run it, but I don't see why Opus wouldn't work on ARM64
> considering it's all C89.

The main issue IIRC is that configure thinks arm64 is capable of compiling 
the standalone arm assembly in celt, which it is not. If that is disabled, 
building should work just fine.

// Martin