[PATCH] Convert signal.h from __need macros to bits/types/ headers.

[Joseph Myers]

On Tue, 6 Dec 2016, Zack Weinberg wrote:

> terrible).  Internal code that wants to manipulate signal masks must
> now include <bits/sigsetops.h> (which is not installed) and should be

The <bits/*.h> naming is only for installed headers.  We renamed various 
stray non-installed bits/ headers there used to be.

-- 
Joseph S. Myers
joseph@codesourcery.com