add missing files to repository
build: avoid bootstrap failure

Without this change, trying to bootstrap GNU sed from a freshly-cloned
Git checkout aborts with an error like this:

  ./bootstrap: aclocal --force -I m4 ...
  ./bootstrap: autoconf --force ...
  configure.ac:20: error: possibly undefined macro: gl_DISABLE_THREADS
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.

* bootstrap.conf (gnulib_modules): Add 'threadlib'.

Copyright-paperwork-exempt: yes
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
tests: enable Automake parallel testsuite harness

It is better than the older test driver.  It is also the default now,
starting from Automake 1.13; so having it enabled unconditionally will
allow GNU sed to be seamlessly bootstrapped by Automake 1.13.

* configure.ac (AM_INIT_AUTOMAKE): Add 'parallel-tests' option.  Also
require Automake 1.11.1, since that is the minimal version to have a
sane 'parallel-tests' support.
(AC_PREREQ): Bump requirement to 2.62, since that is the minimal
version required by Automake 1.11.1.
* testsuite/Makefile.am (TESTS_ENVIRONMENT): Remove the invocation
for the test runner "$(srcdir)/runtest"; it's correct place is ...
(LOG_COMPILER): ... here.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
testsuite: make test logs more verbose

The Automake-provided parallel testsuite harness take care of
redirection the stdout and stderr of the run test cases to a
corresponding log file, so we no longer have to worry about
avoiding to pollute the "make test" output.

* testsuite/runtest: Adjust and simplify.

Copyright-paperwork-exempt: yes
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>