- varchar -> char
- transient_expression -> interval_value
- interval_type -> interval_field


mysql-test/lib/init_db.sql:
  - varchar -> char
  - transient_expression -> interval_value
  - interval_type -> interval_field
scripts/mysql_fix_privilege_tables.sql:
  - varchar -> char
  - transient_expression -> interval_value
  - interval_type -> interval_field
sql/event.h:
  - varchar -> char
  - transient_expression -> interval_value
  - interval_type -> interval_field