CURSOR_TYPE_READ_ONLY". The bug was that we (me) don't perform proper
cleanups of the prepared statement when done fetching from a cursor.
Another patch.


sql/mysql_priv.h:
  Rename reset_stmt_for_execute to init_stmt_before_use (to correspond to
  cleanup_stmt_and_thd_after_use).
sql/sp_head.cc:
  Rename.
sql/sql_prepare.cc:
  Move common cleanup code to a cleanup function, call it when we close
  a cursor.
sql/sql_select.cc:
  Cleanup.
sql/sql_select.h:
  No need for init_thd, this code has been inlined in Cursor::open.
tests/mysql_client_test.c:
  Add a test case for Bug#10729 "mysql_stmt_attr_set CURSOR_TYPE_READ_ONLY"
  (problem reusing a prepared statemnt if there was a cursor)