The warning sent is by itself ok, the problem was rather why it wasn't
  sent on some other platforms...
  The real problem was that a total_warn_count which was inconsistent with warn_list
  was sent back with send_eof() during SP execution, which in turn cause a protocol
  error in mysqltest.


mysql-test/r/sp.result:
  Updated results after fixing bug in how total_warn_count is handled.
sql/protocol.cc:
  Fixed bug that caused protocol errors with mysqltest. Don't send total_warn_count
  with send_eof() during SP execution, as it's usually wrong anyway. (warn_list is
  cleared)
sql/sql_parse.cc:
  Reset total_warn_count if the warn_list has been cleared. This gets rid of
  "empty" warnings after some CALLs.