- Pass "in_comment" variable on to new lex in sp_head::reset_lex
 - Add testcases for dumping and reloading trigger without BEGIN/END


mysql-test/r/mysqldump.result:
  Update test result
mysql-test/t/mysqldump.test:
  Add test for dumping trigger without begin/end, and test that the output from mysqldump can be reloaded.
sql/sp_head.cc:
  If already in a comment before parsing a substatement, set in_comment in the new lex as well.
  This will handle cases where the comment starts before the substatement, which is common in 
  output from mysqldump to mask away syntax not supported by earlier versions of MySQL.
  Ex:
  /*!50003 CREATE TRIGGER `tr1` BEFORE INSERT ON `t1` FOR EACH ROW
  set new.created=now() */;
  ^=== sp_head::reset_lex is called when already in comment