[PATCH] Optimized generic expf and exp2f

[Arjan van de Ven]

> 
> expf reciprocal-throughput: 1.5x faster
> expf latency: 1.4x faster

interesting; the fma existing expf for x86_64 is 10 to 11 cycles reciprocal-throughput ;-)
time to see how you got that 1.5x faster....