REPORT OLD DATETIME FORMAT.

Analysis:
--------
CHECK TABLE FOR UPGRADE does not detect temporal types of
old format. As a result 'mysql_upgrade' does not REPAIR
TABLE/ALTER TABLE FORCE for the tables containing columns
of temporal types old format.

The function 'check_old_type()' checks if the table
contains data types of old format and reports an
error to rebuild the table in order to upgrade the
data types of old format. This function did not
check for the old temporal types and hence did not
report an error.

Fix:
---
a) The function 'check_old_type()' is modified to detect
   old temporal data types if the system variable
   'avoid_temporal_upgrade' is disabled. Hence CHECK TABLE
   FOR UPGRADE reports a rebuild error for upgrading the
   tables. This also helps the 'mysql_upgrade' utility to
   detect and upgrade the tables containing the old temporal
   columns.
b) REPAIR TABLE upgrades the tables containing the old
   temporal types if the 'avoid_temporal_upgrade' system
   variable is disabled.
c) The 'mysql_upgrade' tool has been modified to run the
   'mysql_fix_privilege_tables.sql' and then 'mysqlcheck'.
   This fixes any issues with the tables in the system
   database before running the 'mysqlcheck' on it.