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.

contrib/libgnuregex/regcomp.c

@@ -2664,11 +2664,7 @@ build_range_exp (bitset_t sbcset, bracket_elem_t *start_elem,
       return REG_ECOLLATE;
     cmp_buf[0] = start_wc;
     cmp_buf[4] = end_wc;
-#ifdef __FreeBSD__
-    if (wcscmp (cmp_buf, cmp_buf + 4) > 0)
-#else
     if (wcscoll (cmp_buf, cmp_buf + 4) > 0)
-#endif
       return REG_ERANGE;
 
     /* Got valid collation sequence values, add them as a new entry.
@@ -2710,13 +2706,8 @@ build_range_exp (bitset_t sbcset, bracket_elem_t *start_elem,
     for (wc = 0; wc < SBC_MAX; ++wc)
       {
 	cmp_buf[2] = wc;
-#ifdef __FreeBSD__
-	if (wcscmp (cmp_buf, cmp_buf + 2) <= 0
-	    && wcscmp (cmp_buf + 2, cmp_buf + 4) <= 0)
-#else
 	if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
 	    && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
-#endif
 	  bitset_set (sbcset, wc);
       }
   }

contrib/libgnuregex/regexec.c

@@ -3964,13 +3964,8 @@ check_node_accept_bytes (const re_dfa_t *dfa, int node_idx,
 	    {
 	      cmp_buf[0] = cset->range_starts[i];
 	      cmp_buf[4] = cset->range_ends[i];
-#ifdef __FreeBSD__
-	      if (wcscmp (cmp_buf, cmp_buf + 2) <= 0
-		  && wcscmp (cmp_buf + 2, cmp_buf + 4) <= 0)
-#else
 	      if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
 		  && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
-#endif
 		{
 		  match_len = char_len;
 		  goto check_node_accept_bytes_match;