Fix the testsuite

Fix the testsuite

* tests/sparse05.at: Use autom4te magic to generate mapfile,
instead of the shell command seq, which is not always available.
* tests/listed03.at: Skip the test if xgetcwd fails.
* tests/ckmtime.c: New file.
* tests/Makefile.am: Build ckmtime
* tests/testsuite.at (AT_CHECK_TIMESTAMP): Check whether newly created
files have timestamps consistent with the creation time.  Skip the test
if not.
* tests/incr01.at: Use AT_CHECK_TIMESTAMP
* tests/incr02.at: Likewise.
* tests/incr03.at: Likewise.
* tests/incr04.at: Likewise.
* tests/incr05.at: Likewise.
* tests/incr06.at: Likewise.
* tests/incr07.at: Likewise.
* tests/incr08.at: Likewise.
* tests/incr09.at: Likewise.
* tests/incr10.at: Likewise.
* tests/incr11.at: Likewise.
* tests/incremental.at: Likewise.
* tests/listed01.at: Likewise.
* tests/listed02.at: Likewise.
* tests/listed04.at: Likewise.
* tests/listed05.at: Likewise.