Back out non-collating [a-z] ranges.

Instead of changing the whole course to another POSIX-permitted way
for consistency and uniformity I decide to completely ignore missing
regex fucntionality and focus on fixing bugs in what we have now,
too many small obstacles we have choicing other way, counting ports.
Corresponding libc changes are backed out in r302824.

gnu/usr.bin/grep/dfa.c

@@ -2547,13 +2547,8 @@ match_mb_charset (struct dfa *d, int s, position pos, int index)
       wcbuf[2] = work_mbc->range_sts[i];
       wcbuf[4] = work_mbc->range_ends[i];
 
-#ifdef __FreeBSD__
-      if (wcscmp(wcbuf, wcbuf+2) >= 0 &&
-	  wcscmp(wcbuf+4, wcbuf) >= 0)
-#else
       if (wcscoll(wcbuf, wcbuf+2) >= 0 &&
 	  wcscoll(wcbuf+4, wcbuf) >= 0)
-#endif
 	goto charset_matched;
     }