Merge with coreutils Makefile.maint.

Merge with coreutils Makefile.maint.
(CVS_LIST): Use build-aux version if available.
(VERSION_REGEXP): New macro.
(syntax-check-rules): Add sc_no_if_have_config_h,
sc_prohibit_assert_without_use, sc_require_config_h,
sc_useless_cpp_parens.
(sc_obsolete_symbols): Check for O_NDELAY.
(sc_dd_max_sym_length): Track coreutils.
(sc_unmarked_diagnostics): Look in all files, not just *.c.
(sc_useless_cpp_parens): New rule.
(news-date-check): Look for version or today's date.
(changelog-check): Don't require version number near head.
(copyright-check): Use current year instead of hardwiring 2005.
(my-distcheck): Depend on $(release_archive_dir)/$(prev-tgz).
(announcement): Add --gpg-key-ID.