* configure.ac (CONF_SUBDIRS): Make these relative to

* configure.ac (CONF_SUBDIRS): Make these relative to
tests/Makefile.am.
(DIST_MAKEFILE_LIST): Adjust to compensate for having removed the
`tests/' part in CONF_SUBDIRS.
* tests/Makefile.am (DIST_SUBDIRS): Distribute these directories.
(SUBDIRS): Set to `.', a NOP, to workaround an automake bug which
ignores DIST_SUBDIRS unless SUBDIRS is also set.
* Makefile.am (DIST_SUBDIRS): Don't try to distribute the tests
subdirectories from here, since the recursive automake dist rule
only works with direct child directories.  Defer to
tests/Makefile.am in this case.