[PATCH] Simplify strncat.

[David Miller]

From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 16 Dec 2014 12:50:38 -0800

> Thanks, this is much better than worrying about how to pacify GCC. The
> code could be made a bit shorter and clearer with mempcpy, and there's
> no longer any need to distinguish between s and s1, so I suggest the
> following minor rewrite, which shrinks the code size by another 26
> bytes (16%) on my x86-64 platform.

The fact that we are talking about complete rewrites for what should
be a one line warning fix shows that we enabled -Werror prematurely.

This should have been a no-brainer, yet it is going to take a week to
fix something that is breaking the build for people.