work (prepared statements)" and after-review fixes:
- str_to_TIME renamed to str_to_datetime to pair with str_to_time
- functions str_to_time and str_to_TIME moved to sql-common
- send_data_str now supports MYSQL_TYPE_TIME, MYSQL_TIME_DATE,
  MYSQL_TIME_DATETIME types of user input buffers.
- few more comments in the client library
- a test case added.