CURSOR_TYPE_READ_ONLY date/datetime filter server crash".
The fix adds support for Item_change_list in cursors (proper rollback
of the modified item tree). 


sql/sql_class.cc:
  No need to call fatal_error() twice.
sql/sql_prepare.cc:
  - implement proper cleanup of the prepared statement in mysql_stmt_reset
    if there is a cursor.
  - take into account thd->change_list when fetching data through a
    cursor.
sql/sql_select.cc:
  - take into account thd->change_list when fetching data from a cursor:
    grab it when we open a cursor, and rollback the changes to the parsed
    tree when we close it.
sql/sql_select.h:
  - Cursor::change_list added
tests/mysql_client_test.c:
  - a test case for Bug#11172 "mysql_stmt_attr_set CURSOR_TYPE_READ_ONLY date/datetime
   filter server crash"