Request : FloatVectorOperation::abs()?

a request : would be great to have absolute value methods in FloatVectorOperations. It's a pretty common operation in audio/control

Surely there's some SIMD stuff for abs() no?

I think SSE3 has intrinsics for abs(), but in SSE2 you'd use a masking trick (eg http://aggregate.org/MAGIC/#Absolute%20Value%20of%20a%20Float).

Thank you fabian for the recent commit!