There is an inconsistency with DROP DATABASE IF EXISTS, DROP
TABLE IF EXISTS and DROP VIEW IF EXISTS: those are binlogged even
if the DB or TABLE does not exist, whereas DROP PROCEDURE IF
EXISTS does not. It would be nice or at least consistent if DROP
PROCEDURE/STATEMENT worked the same too.
      
Fixed DROP PROCEDURE|FUNCTION IF EXISTS by adding a call to
write_bin_log in mysql_execute_command. Checked also if all
documented "DROP (...) IF EXISTS" get binlogged. Left out DROP
SERVER IF EXISTS because it seems that it only gets binlogged when
using row event (see BUG#25705).