[MySQL] Avoid confusing label and IPv6 address (#3606)

Some label combined with some keywords (when written without a space
in between, which is valid for MySQL) can look like beginning of an IPv6
address, e.g.

    aaa:BEGIN

is currectly parsed as IPv6 address `aaa:be` and leads to a parsing
failure.

Make parsing of IPv6 address more robust and require at least two `:`
to make sure there is no confusion with labels.

sql/mysql/Positive-Technologies/MySqlLexer.g4

@@ -1320,7 +1320,7 @@ STRING_USER_NAME:                    (
                                      );
 IP_ADDRESS:                          (
                                        [0-9]+ '.' [0-9.]+
-                                       | [0-9A-F:]+ ':' [0-9A-F:]+
+                                       | [0-9A-F]* ':' [0-9A-F]* ':' [0-9A-F:]+
                                      );
 LOCAL_ID:                               '@'
                                      (

sql/mysql/Positive-Technologies/examples/ddl_alter.sql

@@ -102,6 +102,8 @@ alter definer = current_user sql security invoker view my_view4(c1, 1c, _, c1_2)
 -- Alter user
 ALTER USER 'mattias.hultman' DEFAULT ROLE `prod-spain-mysql-read-only`@`%`;
 rename user user1@100.200.1.1 to user2@100.200.1.2;
+rename user user1@100.200.1.1 to user2@2001:0db8:85a3:0000:0000:8a2e:0370:7334;
+rename user user1@100.200.1.1 to user2@::1;
 alter user 'user'@'%' IDENTIFIED BY 'newpassword' RETAIN CURRENT PASSWORD;
 ALTER USER 'test_dual_pass'@'%' IDENTIFIED BY RANDOM PASSWORD RETAIN CURRENT PASSWORD;
 ALTER USER 'test_dual_pass'@'%' IDENTIFIED BY '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' RETAIN CURRENT PASSWORD;

sql/mysql/Positive-Technologies/examples/ddl_create.sql

@@ -450,6 +450,18 @@ BEGIN
 END -- //-- delimiter ;
 #end
 #begin
+-- delimiter //
+CREATE PROCEDURE doiterate(p1 INT)
+-- label which can be parsed as a beginning of IPv6 address
+aaa:BEGIN
+  label1:LOOP
+    SET p1 = p1 + 1;
+    IF p1 < 10 THEN ITERATE label1; END IF;
+    LEAVE label1;
+  END LOOP label1;
+END -- //-- delimiter ;
+#end
+#begin
 CREATE DEFINER=`system_user`@`%` PROCEDURE `update_order`(IN orderID bigint(11))
 BEGIN  insert into order_config(order_id, attribute, value, performer)
        SELECT orderID, 'first_attr', 'true', 'AppConfig'
@@ -659,4 +671,4 @@ DECLARE array VARCHAR(50);
 SELECT 1;
 
 END
-#end
+#end