am efac088b: Merge remote-tracking branch \'toybox/master\' into HEAD

am efac088b: Merge remote-tracking branch \'toybox/master\' into HEAD

* commit 'efac088b31902aaf676952d8b9beedab270d9a2d': (28 commits)
  Kylie McClain pointed out that -z affects both input and output.
  Actually set time with touch -d and -t when you don't specify nanonseconds.
  First pass on cp --preserve
  Promote xxd to other.
  Probe for fork() instead of relying on a distro-specific #define.
  Added i option to use other interface on running dhcpd.
  Cleanup xxd.
  Minor cleanups on xxd.
  The android guys sent in xxd. It doesn't share code with od and hexdump. Hmmm...
  Fix segfault with "mount -o ro,remount".
  Improve -Z error reporting.
  Fix top.c build.
  mkfifo -Z
  Add ionice and iorenice.
  Add undo buffer for 'u'.
  Simplify hexedit logic by adjusting viewport all in one place up top. (Easier to genericize logic and reuse later in less or vi...)
  Factor out more not-curses infrastructure into lib.
  Suggestion from Elliott Hughes: tweak test infrastructure to notice if command exits with high errno and assume it segfaulted.
  Fix version number in ifconfig cleanup reference.
  Don't segfault if none of the file arguments to ls exists.
  ...