with cursor". The patch refactors do_select/sub_select
functions, which implement the nested loop algorithm, and reuses them to
fetch rows for cursors as well.
Pushing with view.test failing (--ps-protocol).


sql/sql_prepare.cc:
   Cursor::fetch() now returns void
sql/sql_select.cc:
  A fix for Bug#9520 "SELECT DISTINCT crashes server with cursor":
  * rename sub_select returns codes to be able to track down what's going
    on in which case.
  * move record processing and outer join record processing to a separate
    function, out of sub_select read-record loop.
  * use generalized sub_select() nested loop function for
  cursors instead of own loop implementation used in Cursor::fetch() before
sql/sql_select.h:
  Replace all return values of sub_select family with enum.
  Add JOIN::resume_nested_loop flag to indicate we are restarting the nested loop
  for execution of next chunk of cursor's rows.
tests/mysql_client_test.c:
  A test case for Bug#9520 "SELECT DISTINCT crashes server with cursor"