[PATCH v2] Replace use of snprintf with strfrom in libm tests

[Joseph Myers]

On Mon, 19 Dec 2016, Gabriel F. T. Gomes wrote:

>   - Use totalorder in fmt_ftostr to detect if the floating-point
>     number being printed is non-negative, then add a leading space.

Surely signbit is the appropriate thing to use here (much simpler and 
obviously correct), not totalorder....

-- 
Joseph S. Myers
joseph@codesourcery.com