Import atf-0.21:

Released on October 23rd, 2014.

* Restored the atf(7) manual page to serve as a reference to all the other
  manual pages shipped by ATF.

* Added the -s flag to atf-sh to support specifying the shell interpreter
  to be used.

* Removed ATF_WORKDIR.  The only remaining consumers have been converted to
  use the standard TMPDIR environment variable.  As a benefit, and because
  Kyua forces the TMPDIR to live within the test case's work directory,
  any stale files left behind by ATF will be automatically cleaned up.

* Documented the environment variables recognized by each component in the
  relevant manual pages.  This information was lost with the atf-config(1)
  removal.

* Added a new "require.diskspace" metadata property to test cases so that
  they can specify the minimum amount of disk space required for the test
  to run.

* Renamed the atf-{c,c++,sh}-api(3) manual pages to atf-{c,c++,sh}(3) for
  discoverability purposes.  Symbolic links are provided for the time
  being to still make the old names visible.

* Issue #5: Recommend the (expected, actual) idiom for calls to the test
  macros in the manual pages.

* Issue #7: Stopped catching unhandled exceptions in atf-c++ tests.  This
  propagates the crash to the caller, which in turn allows it to obtain
  proper debugging information.  In particular, Kyua should now be able to
  extract a stacktrace pinpointing the problem.

* Issue #8: Fixed atf-c/macros_test:use test failures spotted by the clang
  that ships with FreeBSD 11.0-CURRENT.

* Issue #12: Improved documentation of atf-sh(3) and atf-check(1) by better
  explaining how they relate to each other.

* Issue #14: Stopped setting 'set -e' in atf-sh.  This setting was
  initially added as a way to enable a "strict" mode in the library and to
  make test cases fail fast when they run unprotected commands.  However,
  doing so in the library is surprising as the responsibility of enabling
  'set -e' should be on the user's code.  Also, 'set -e' introduces
  inconsistent behavior on subshells and users do not expect that.

* Issue #15: Fixed atf_utils_{fork,wait} to support nested calls.

* Issue #16: Fixed test failures (by removing a long-standing hack) on
  systems that lack \e support in printf(1).

* Issue #19: Removed stale references to atf-config and atf-run.
Put mtree test files into a subdirectory.

Kyua 0.11 points TMPDIR to the test's work directory, and atf_check creates
auxiliary files in TMPDIR.  This confuses a couple of mtree tests that were
using the work directory's root to validate the contents of the directory.

Fix the two affected tests by creating an auxiliary directory to use for
the mtree tests.  (Kyua should probably do this on its own; filed bug #133
upstream to take a look at this.)
MFV: Import atf-0.21.