Upgrade was a reserved word. Unreserve UPGRADE so it can be used in unquoted identifiers.


mysql-test/r/create.result:
  Bug #21772: can not name a column 'upgrade' when create a table in version 5.0.24
   - test case
mysql-test/t/create.test:
  Bug #21772: can not name a column 'upgrade' when create a table in version 5.0.24
   - test case
sql/sql_yacc.yy:
  Bug #21772: can not name a column 'upgrade' when create a table in version 5.0.24
   - unreserve UPGRADE.