fp printing speedup, take 3

[Paolo Carlini]

Benjamin Kosnik wrote:

> Yo dude. Sorry for the wait.
>
> This passes on x86/linux. I'm testing on powerpc at the moment.
>
> I have to work out the cross-configure bits. I'm also not quite sure
> about the quad configury.
>
> But, most of the rest of it is done.

Great work Benjamin (and Jerry)!
I look forward to see the whole thing committed.

Paolo.

P.S. I'm putting on hold my fix for grouping vs floats missing the
decimal point (will be faster and more clean thanks to info
already computed by the new code!)