Remove the following obsolete SQL modes:

 * MODE_POSTGRESQL
 * MODE_ORACLE
 * MODE_MSSQL
 * MODE_DB2
 * MODE_NO_KEY_OPTIONS
 * MODE_NO_TABLE_OPTIONS
 * MODE_NO_FIELD_OPTIONS
 * MODE_MYSQL323
 * MODE_MYSQL40

Trying to set any of these, even as numeric values, will now give a hard error.

MODE_MAXDB will be removed in a separate step, as it requires parser changes.

Change-Id: I81219a41999539900d1bde0307c7b7d3d553cc77