[m-rev.] write_float_special.exp4

[Zoltan Somogyi]

On my laptop, the output of the hardcoded/write_float_special test has long been:

Inf: inf
-Inf: -inf
NaN: -nan

The expected output does not have the - sign in front of the nan.

I don't particularly care about the exact details of how we format non-number
numbers, but having a test case always failing is annoying.

I think either the MR_is_nan test should be moved earlier in MR_sprintf_float,
to before the - is printed, or the output above should be added as tests/
hardcoded/write_float_special.exp4, with corresponding .exp[56] for infinity/
Infinity. What do others think?

Zoltan.