Run "make update-copyright" and then...
* tests/sample-test: Adjust to use the single most recent year.
* tests/du/bind-mount-dir-cycle-v2.sh: Fix case in copyright message,
so that year is updated automatically in future.
If we can't output more data, we should immediately
diagnose the issue and exit rather than consuming all
of input (in some cases).
* src/tail.c (xwrite_stdout): Also diagnose the case where
only some data is written. Also clearerr() to avoid the
redundant less specific error from atexit (close_stdout);
* src/head.c (xwrite_stdout): Copy this new function from tail,
and use it to write all output.
* tests/misc/head-write-error.sh: A new test to ensure we
exit immediately on write error.
* tests/local.mk: Reference the new test.
