[patch/rfc] Add host's floatformat

[DJ Delorie]

> Like this?  I feel ill.

One problem with your approach is that "1.0" may not be a suitable
pattern to match for every FPU.  I left the test constant in the
structure because some FPUs may need more esoteric patterns to
differentiate themselves from other FPUs.  Hence the comment about
keeping them in order, too.

Again, libiberty patches must be posted to gcc-patches@gcc.gnu.org as
well as wherever else.