* tests/local.mk (tests/atconfig): The rule was incorrect, but
remove it: now that there is no tests/Makefile.am, the top-level
Makefile properly updates atconfig when needed.
TESTSUITEFLAGS is barely readable.
* tests/local.mk (TESTSUITE_FLAGS): Default to $(TESTSUITEFLAGS)
for backward compatibility.
Use the former instead of the latter.
* tests/Makefile.am: Rename as...
* tests/local.mk: this.
* Makefile.am, configure.ac: Adjust.
* Makefile.am (DISTCLEANFILES): Define.
(maintainer-check, maintainer-xml-check, maintainer-push-check):
Remove, we no longer need to bounce to the real targets.