if the function, invoked in a non-binlogged caller (e.g. SELECT, DO), failed half-way on the master,
slave would stop and complain that error code between him and master mismatch. 
To solve this, when a stored function is invoked in a non-binlogged caller (e.g. SELECT, DO), we binlog the function
call as SELECT instead of as DO (see revision comment of sp_head.cc for more).
And: minor wording change in the help text.
This cset will cause conflicts in 5.1, I'll merge.


mysql-test/r/rpl_sp.result:
  result update
mysql-test/t/rpl_sp-slave.opt:
  bug just fixed so option not needed
mysql-test/t/rpl_sp.test:
  test for more half-failed functions with DO and SELECT, to test the bug of this changeset.
  cleanup at the end.
sql/mysqld.cc:
  function -> stored function (change suggested by Paul)
sql/sp_head.cc:
  When a function updates data and is called from a non-binlogged statement (SELECT, DO), we binlog it 
  as SELECT myfunc(), and not DO myfunc() like before.