[MysqlCompatibility] Support convert() function and signed/unsigned integer

[morningman]

Describe the bug

To support following sql:

SELECT TABLE_SCHEMA TABLE_CAT, NULL TABLE_SCHEM, TABLE_NAME, COLUMN_NAME, CASE data_type WHEN 'bit' THEN -7 WHEN 'tinyblob' THEN -3 WHEN 'mediumblob' THEN -4 WHEN 'longblob' THEN -4 WHEN 'blob' THEN -4 WHEN 'tinytext' THEN 12 WHEN 'mediumtext' THEN -1 WHEN 'longtext' THEN -1 WHEN 'text' THEN -1 WHEN 'date' THEN 91 WHEN 'datetime' THEN 93 WHEN 'decimal' THEN 3 WHEN 'double' THEN 8 WHEN 'enum' THEN 12 WHEN 'float' THEN 7 WHEN 'int' THEN IF( COLUMN_TYPE like '%unsigned%', 4,4) WHEN 'bigint' THEN -5 WHEN 'mediumint' THEN 4 WHEN 'null' THEN 0 WHEN 'set' THEN 12 WHEN 'smallint' THEN IF( COLUMN_TYPE like '%unsigned%', 5,5) WHEN 'varchar' THEN 12 WHEN 'varbinary' THEN -3 WHEN 'char' THEN 1 WHEN 'binary' THEN -2 WHEN 'time' THEN 92 WHEN 'timestamp' THEN 93 WHEN 'tinyint' THEN IF(COLUMN_TYPE like 'tinyint(1)%',-7,-6)  WHEN 'year' THEN 91 ELSE 1111 END  DATA_TYPE, IF(COLUMN_TYPE like 'tinyint(1)%', 'BIT',  UCASE(IF( COLUMN_TYPE LIKE '%(%)%', CONCAT(SUBSTRING( COLUMN_TYPE,1, LOCATE('(',COLUMN_TYPE) - 1 ), SUBSTRING(COLUMN_TYPE ,1+locate(')', COLUMN_TYPE))), COLUMN_TYPE))) TYPE_NAME,  CASE DATA_TYPE  WHEN 'time' THEN IF(DATETIME_PRECISION = 0, 10, CAST(11 + DATETIME_PRECISION as signed integer))  WHEN 'date' THEN 10  WHEN 'datetime' THEN IF(DATETIME_PRECISION = 0, 19, CAST(20 + DATETIME_PRECISION as signed integer))  WHEN 'timestamp' THEN IF(DATETIME_PRECISION = 0, 19, CAST(20 + DATETIME_PRECISION as signed integer))  ELSE   IF(NUMERIC_PRECISION IS NULL, LEAST(CHARACTER_MAXIMUM_LENGTH,2147483647), NUMERIC_PRECISION)  END COLUMN_SIZE, 65535 BUFFER_LENGTH,  CONVERT (CASE DATA_TYPE WHEN 'year' THEN NUMERIC_SCALE WHEN 'tinyint' THEN 0 ELSE NUMERIC_SCALE END, UNSIGNED INTEGER) DECIMAL_DIGITS, 10 NUM_PREC_RADIX, IF(IS_NULLABLE = 'yes',1,0) NULLABLE,COLUMN_COMMENT REMARKS, COLUMN_DEFAULT COLUMN_DEF, 0 SQL_DATA_TYPE, 0 SQL_DATETIME_SUB,   LEAST(CHARACTER_OCTET_LENGTH,2147483647) CHAR_OCTET_LENGTH, ORDINAL_POSITION, IS_NULLABLE, NULL SCOPE_CATALOG, NULL SCOPE_SCHEMA, NULL SCOPE_TABLE, NULL SOURCE_DATA_TYPE, IF(EXTRA = 'auto_increment','YES','NO') IS_AUTOINCREMENT,  IF(EXTRA in ('VIRTUAL', 'PERSISTENT', 'VIRTUAL GENERATED', 'STORED GENERATED') ,'YES','NO') IS_GENERATEDCOLUMN  FROM INFORMATION_SCHEMA.COLUMNS  WHERE (ISNULL(database()) OR (TABLE_SCHEMA = database())) AND (TABLE_NAME = 'tbl2') AND (1 = 1) ORDER BY TABLE_CAT, TABLE_SCHEM, TABLE_NAME, ORDINAL_POSITION;

We need to support:

1. convert() functin
2. signed/unsigned keywords