Draft "Unsafe fp optimizations" project description.

[Gabriel Dos_Reis]

| <<If that point were to be considered or included in the discussion, it
| would be a good thing to provide a list of supported plateforms where
| intermediate results use or do not use extra precision (e.g. x86-like
| vs. Sparc-like).
| >>
| 
| There are two cases, extended real for 64-bit, this obviously only
| happens on Intel architectures, since no others support this :-)
| 
| But the other csae is 64-bit for 32-bit, and that arises on a much
| wider range of architectures, e.g. Power

Yes, still we need to have a list of such supported plateforms; for
future reference.

-- Gaby