[PULL] XQuartz {Add,Remove}EnabledDevice build fixes and other cleanup

[Adam Jackson]

On Tue, 2016-09-13 at 10:09 -0700, Jeremy Huddleston Sequoia wrote:

> Yes, if it is a relative path, things might not go the way we want
> them to, so that's a good point.  The related logic in libxcb has the
> same issue.  If this is something we want to squash, we should do it
> in both places by changing 'if (display_env)' to 'if (display_env &&
> *display_env == '/')'
> 
> Would that make you feel more comfortable?

Yeah. Maybe if we wanted relative paths we'd want to do
strchr(display_env, '/'), but like I say, having a hard time coming up
with a good reason to want that.

- ajax