[PATCH 0/2] Fix or silence "unused result" warnings

[Austin Clements]

I'm afraid I bikeshedded dme's original patch for this into oblivion
(id:"1324503532-5799-1-git-send-email-dme at dme.org") and we still have
these warnings on the buildbot.  Tomi convinced me that dme was right
and I was wrong, so I'm bringing dme's patch back.

The first patch actually fixes the warning, since the code in show was
wantonly ignoring errors that could have correctness implications.
This write didn't get much attention in the original thread.

The second is a rework of dme's patch to silence the warning for the
remaining writes.  I cleaned up the formatting, simplified the macro
magic a little, and added a comment justifying its use.