This is a regression from 2007-05-18 when code to zero out the returned struct was
added to number_to_datetime(); zero for time_type corresponds to MYSQL_TIMESTAMP_DATE.
We now explicitly set the type we return (MYSQL_TIMESTAMP_DATETIME).


mysql-test/r/func_time.result:
  show that DATE_ADD() behaves the same for YYYYMMDDhhmmss given
  as string and as integer.
mysql-test/t/func_time.test:
  show that DATE_ADD() behaves the same for YYYYMMDDhhmmss given
  as string and as integer.
sql-common/my_time.c:
  explictly set return type in number_to_datetime()