Parsing "@@" throws exception

[Aceto1]

Describe the bug
When parsing the below SQL an exception with the message: "Not yet supprted" is thrown. This is totally valid MariaDB SQL Syntax that runs just fine when directly executing on the database.

To Reproduce
Steps to reproduce the behavior:

1. SQL: "SET @@global.time_zone = '01:00'"
2. Parsing this SQL using JSqlParser with this statements
3. Exception:

Encountered unexpected token: "@@" "@@"
    at line 1, column 5.

Was expecting one of:

    "ACTION"
    "ANY"
    "BYTE"
    "CASCADE"
    "CAST"
    "CHANGE"
    "CHAR"
    "CHARACTER"
    "COLUMN"
    "COLUMNS"
    "COMMENT"
    "COMMIT"
    "CREATE"
    "CYCLE"
    "DESC"
    "DESCRIBE"
    "DISABLE"
    "DIV"
    "DO"
    "DOUBLE"
    "DUPLICATE"
    "ENABLE"
    "END"
    "EXCLUDE"
    "EXTRACT"
    "FALSE"
    "FIRST"
    "FN"
    "FOLLOWING"
    "FORMAT"
    "GROUP"
    "IF"
    "INDEX"
    "INSERT"
    "INTERVAL"
    "ISNULL"
    "KEY"
    "LAST"
    "LEFT"
    "LIMIT"
    "MATERIALIZED"
    "NEXTVAL"
    "NO"
    "NOLOCK"
    "NULLS"
    "OF"
    "OFFSET"
    "ON"
    "OPEN"
    "OPTIMIZE"
    "ORDER"
    "OVER"
    "PARTITION"
    "PATH"
    "PERCENT"
    "PRECISION"
    "PRIMARY"
    "PRIOR"
    "PROCEDURE"
    "PUBLIC"
    "RANGE"
    "READ"
    "REPLACE"
    "RIGHT"
    "ROW"
    "ROWS"
    "SCHEMA"
    "SEPARATOR"
    "SEQUENCE"
    "SESSION"
    "SET"
    "SIBLINGS"
    "SIZE"
    "START"
    "TABLE"
    "TABLES"
    "TEMP"
    "TEMPORARY"
    "TO"
    "TOP"
    "TRUE"
    "TRUNCATE"
    "TYPE"
    "UNSIGNED"
    "VALIDATE"
    "VALUE"
    "VALUES"
    "VIEW"
    "XML"
    "ZONE"
    <K_DATETIMELITERAL>
    <K_DATE_LITERAL>
    <S_IDENTIFIER>
    <S_QUOTED_IDENTIFIER>

Expected behavior
The statement should be parsed just fine, since it is a valid SQL statement for MariaDB

System

• MariaDB 10.5.8
• Java 11
• JSqlParser version 4.0

[wumpz]

This kind of "user variable" is not yet supported.