[feature] complete syntax about 'TRUNCATE/DROP TABLE Statement'

[hustjieke]

For TRUNCATE In MySQL 8.0 syntax:

TRUNCATE [TABLE] tbl_name

In Radon now syntax:

TRUNCATE TABLE table_name

For DROP in MySQL 8.0:

DROP [TEMPORARY] TABLE [IF EXISTS]
    tbl_name [, tbl_name] ...
    [RESTRICT | CASCADE]

In radon now support:

DROP TABLE [IF EXISTS] table_name