CURSOR_TYPE_READ_ONLY nested queries corrupt result"


sql/sql_prepare.cc:
  If there is a cursor, use its protocol for fetch: 
  Protocol instances have a state and thd->protocol_prep can't
  be used for multiple cursors.
sql/sql_select.cc:
  - init Cursor::protocol
sql/sql_select.h:
  - add Cursor::protocol
tests/mysql_client_test.c:
  A test case for Bug#11909 "mysql_stmt_attr_set CURSOR_TYPE_READ_ONLY
   nested queries corrupt result"