Parallel "make check" support.

Parallel "make check" support.

* build-aux/check.mk: New file, from The Vaucanson Group.
* .x-sc_GPL_version: New file, to allow "version 2 or later"
in build-aux/check.mk.
* Makefile.am (EXTRA_DIST): Add .x-sc_GPL_version.
* tests/check.mk: New file.
* tests/Makefile.am (EXTRA_DIST): Add check.mk, mkdtemp and test-lib.sh.

Begin factoring "sample-test" out of test scripts.
* tests/test-lib.sh: New file, to be sourced by all tests that
were previously derived from the "sample-test" template.
* tests/mkdtemp: New file.
* tests/touch/dir-1: Use test-lib.sh.
* tests/touch/empty-file: Likewise.
* tests/touch/fail-diag: Likewise.
* tests/touch/fifo: Likewise.
* tests/touch/no-create-missing: Likewise.
* tests/touch/no-rights: Likewise.  Also, don't sleep.
* tests/touch/not-owner: Likewise.
* tests/touch/obsolescent: Likewise.
* tests/touch/read-only: Likewise.
* tests/touch/relative: Likewise.
* tests/touch/Makefile.am: Include $(top_srcdir)/tests/check.mk,
to get the parallel-"make check" bits.

Move a slow test into tests/misc.

* tests/check.mk: Wrapper.
* tests/ls/time-1: Move this file to tests/misc/ls-time.
* tests/misc/ls-time: New file.  From tests/ls/time-1.
* tests/ls/Makefile.am (TESTS): Remove time-1.
* tests/misc/Makefile.am (TESTS): Add ls-time.