Miscellaneous sys/ucontext.h namespace fixes (bug 21457)

[Joseph Myers]

On Mon, 26 Jun 2017, Zack Weinberg wrote:

> > 	* sysdeps/unix/sysv/linux/sparc/
> The SPARC changes are complicated enough that I think they need to be
> reviewed by an architecture maintainer.

Architecture maintainer ping for the SPARC parts of 
<https://sourceware.org/ml/libc-alpha/2017-06/msg00875.html>....

-- 
Joseph S. Myers
joseph@codesourcery.com