be more flexible in what we accept for char based dtmf (ABCD and abcd), patch…

be more flexible in what we accept for char based dtmf (ABCD and abcd), patch from George Shaw.  Thanks.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@4197 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/switch_utils.c

@@ -397,6 +397,7 @@ SWITCH_DECLARE(unsigned char) switch_char_to_rfc2833(char key)
     char *c;
 	unsigned char counter = 0;
 
+    key = (char)toupper(key);
     for (c = RFC2833_CHARS; *c ; c++) {
         if (*c == key) {
             return counter;