[PATCH] Fix truncf for sNaN input

[Joseph Myers]

On Mon, 16 Mar 2020, Keith Packard via Newlib wrote:

> I was concerned with what NaN values are delivered from a NaN
> operand, given the POSIX specification which says that the operand
> itself shall be delivered if it is a NaN.

I don't think POSIX specifications should be trusted for how functions 
should behave with sNaN inputs.  Rather, prefer the specifications from TS 
18661-1 (or the latest C2x draft which has TS 18661-1 integrated).

-- 
Joseph S. Myers
joseph@codesourcery.com