branch-1_4 error message cleanup

[Eric Blake]

Now that gnulib has verror, I checked in the patch here:
http://lists.gnu.org/archive/html/m4-discuss/2006-08/msg00004.html

I wanted to do this, too, to avoid "m4:NONE:0: message" for things like `m4 -R 
none' or `echo "m4wrap(\`dnl()')"|m4':

verror_at_line (status, errnum, current_line ? current_file : NULL,
                current_line, message, args);

but glibc currently has a bug that it results in "m4:message" rather than the 
desired "m4: message" of the GNU Coding Standards 
(http://sourceware.org/bugzilla/show_bug.cgi?id=2997).  So for now, I've just 
left the NONE:0: in messages, to avoid spurious testsuite differences caused by 
users with buggy glibc.

-- 
Eric Blake