#10 Aften fails to build under arm64 macOS

[Ryan Carsten Schmidt]

Trying to build aften 0.0.8 for arm64 on a new Mac powered by Apple Silicon fails:

libaften/a52enc.c:373:5: error: implicit declaration of function 'apply_simd_restrictions' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    apply_simd_restrictions(&s->system.wanted_simd_instructions);
    ^
1 error generated.

There are, unsurprisingly given this project's age, only Intel and PowerPC implementations of apply_simd_restrictions in the code.