(CVS_LIST): Don't assume cvsu is available.

(CVS_LIST): Don't assume cvsu is available.
(CVS_LIST_EXCEPT): New macro, to simplify exception-processing.
Most uses of CVS_LIST changed to use CVS_LIST_EXCEPT.
(syntax-check-rules): Bring back sc_changelong.  (Hmm, why did it
go away? was that an accident?)
(sc_cast_of_argument_to_free, sc_cast_of_x_alloc_return_value):
(sc_cast_of_alloca_return_value, sc_space_tab, sc_prohibit_atoi_atof):
(sc_error_exit_success, sc_file_system, sc_no_if_have_config_h):
(sc_system_h_headers, sc_sun_os_names, sc_trailing_blank):
(sc_two_space_separator_in_usage, sc_unmarked_diagnostics):
(sc_obsolete_symbols, sc_changelog, sc_prohibit_jm_in_m4):
(sc_useless_cpp_parens, makefile-check, m4-check, po-check):
(author_mark_check, makefile_path_separator_check):
Output line numbers, to simplify navigation of Emacs *compilation*
buffers.
(sc_prohibit_atoi_atof, sc_file_system):
Rework slightly so that Makefile.maint doesn't get reported as a
violation of its own syntax rules.
(sc_dd_max_sym_length): Use ifneq to do nothing, instead of doing
it at run-time (which didn't work with Bison).  Fix a makefile typo,
caught by Makefile.maint itself: spaces where a tab should be.
(po-check): Check lib/*.[ch] even if not in CVS; used by Bison,
which copies from ../gnulib/lib/*.[ch] to lib/*.[ch].
Ignore djgpp and man subdirectories, to avoid false matches with
Bison and coreutils, respectively.  Use sort -u to remove the
resulting duplicates.