Optimising std::find on x86 and PPC

[Paolo Carlini]

Paolo Carlini wrote:

> Besided what Gaby and Benjamin already replied, out of curiosity, what 
> the loop
> unroller is doing, right now?!? Nothing!?!

More explicitly, and in the "right" spirit for the library: let's 
suppose we remove completely any ad-hoc loop-unrolling by hand, can we 
trust the loop-unroller to do a decent work both on x86-linux and 
darwin-powerpc? This is something worth
investigating, IMHO... and in case the loop unroller does crazy things 
file immediately a PR.

Paolo.