open cursor after mysql_stmt_execute" + post-review fixes.
The bug was caused by wrong flags in stmt->server_status on the client
side: if there was no cursor, the server didn't send server_status
flags to the client, and the old flags were used to set up the
fetch function of a statement. Consequently, stmt_read_row_from_cursor was
used when there was no cursor. The fix fixes the server to always
send server flags to the client.


include/mysql_com.h:
  Update stale comments.
libmysql/libmysql.c:
  Remove an extra assignment.
libmysqld/lib_sql.cc:
  Update to correspond to the changed signature of send_eof
sql/protocol.cc:
  Actual fix for bug#10794: create a function that writes the eof
  packet to network and use it from send_fields. We need to send
  a full eof packet from send_fields to inform the client about
  the cursor status (that there is no cursor in this case).
sql/protocol.h:
  Remove an unused parameter for send_eof.
tests/mysql_client_test.c:
  A test case for Bug#10794 "mysql_stmt_attr_set no open cursor 
  after mysql_stmt_execute"