wildmatch: fold bracket-expression pattern chars under force_lower_case

dowild()'s literal path folds the pattern char, but the [class]/[a-z] path
compared unfolded pattern bytes against the (folded) text, so iwildmatch() was
still case-asymmetric for character classes and ranges -- e.g. a daemon
'hosts deny = [A-Z]*.EVIL.COM' failed to match a lower-case host (access-control
fail-open, same class as the literal case).  Fold p_ch for the escaped-member,
range-endpoint and plain-member comparisons; the range start (prev_ch) picks up
the folded value too.  Only active under force_lower_case (iwildmatch), so
case-sensitive wildmatch() is unchanged.

Reported-by: Leonid Bugaev
(cherry picked from commit d443e8dc93)

lib/wildmatch.c

@@ -150,6 +150,8 @@ static int dowild(const uchar *p, const uchar *text, const uchar*const *a)
 		    p_ch = *++p;
 		    if (!p_ch)
 			return ABORT_ALL;
+		    if (force_lower_case && ISUPPER(p_ch))
+			p_ch = tolower(p_ch);
 		    if (t_ch == p_ch)
 			matched = TRUE;
 		} else if (p_ch == '-' && prev_ch && p[1] && p[1] != ']') {
@@ -159,6 +161,8 @@ static int dowild(const uchar *p, const uchar *text, const uchar*const *a)
 			if (!p_ch)
 			    return ABORT_ALL;
 		    }
+		    if (force_lower_case && ISUPPER(p_ch))
+			p_ch = tolower(p_ch);
 		    if (t_ch <= p_ch && t_ch >= prev_ch)
 			matched = TRUE;
 		    p_ch = 0; /* This makes "prev_ch" get set to 0. */
@@ -216,8 +220,12 @@ static int dowild(const uchar *p, const uchar *text, const uchar*const *a)
 		    } else /* malformed [:class:] string */
 			return ABORT_ALL;
 		    p_ch = 0; /* This makes "prev_ch" get set to 0. */
-		} else if (t_ch == p_ch)
-		    matched = TRUE;
+		} else {
+		    if (force_lower_case && ISUPPER(p_ch))
+			p_ch = tolower(p_ch);
+		    if (t_ch == p_ch)
+			matched = TRUE;
+		}
 	    } while (prev_ch = p_ch, (p_ch = *++p) != ']');
 	    if (matched == special || t_ch == '/')
 		return FALSE;