This patch adds PACKAGE support with SQL/PSM dialect for sql_mode=DEFAULT:

- CREATE PACKAGE
- DROP PACKAGE
- CREATE PACKAGE BODY
- DROP PACKAGE BODY
- Package function and procedure invocation from outside of the package:
    -- using two step identifiers
    SELECT pkg.f1();
    CALL pkg.p1()

    -- using three step identifiers
    SELECT db.pkg.f1();
    CALL db.pkg.p1();

This is a non-standard MariaDB extension.

However, later this code can be used to implement
the SQL Standard and DB2 dialects of CREATE MODULE.