Add the promised support of security group functionality in except ban { }

So now the example in the release notes actually works:
except ban {
    mask { security-group irccloud; }
    type { blacklist; connect-flood; handshake-data-flood; }
}

include/struct.h

@@ -1106,6 +1106,7 @@ struct Spamfilter {
 struct BanException {
 	char *usermask; /**< User mask */
 	char *hostmask; /**< Host mask */
+	SecurityGroup *match; /**< Security group (for config file items only) */
 	unsigned short subtype; /**< See TKL_SUBTYPE_* */
 	char *bantypes; /**< Exception types */
 	char *reason; /**< Reason */