maintcheck: consistency of list of test scripts

maintcheck: consistency of list of test scripts

* CheckListOfTests.am: New file.
(maintainer-check-list-of-tests): New target,
check for consistency between list of tests defined in the
including Makefile and list of tests on the filesystem.
(clean-maintcheck-testslist-tmp): New rule, to clean up the
temporary files that might be left around by the rules associated
with the previous target.
(clean-local): Depend on it.
* lib/Automake/tests/Makefile.am: Include `CheckListOfTests.am'.
(maintainer-check): Added dependency from the new target
`maintainer-check-list-of-tests'.
* tests/Makefile.am: Likewise.
* Makefile.am (maintainer-check-list-of-test): New target,
calling recursively into `tests/' and `lib/Automake/tests/',
using ...
(TEST_SUBDIRS): ... this new variable.