Tail fixes after re-applying patches to older version of clone.


sql/log_event.cc:
  Name change of shall_skip() -> do_shall_skip()
  Introducing public shall_skip().
  Name change of skip reason enumeration constants.
  Removing extreneous argument to slave_print_msg() causing compiler warning.
sql/log_event.h:
  Adding enumeration for skip reason.
  Factoring out exec_event() into exec_relay_log_event().
  Making public interface to event execution primitives.
  Adding documentation.
  Making some (internal) functions const-correct.
sql/rpl_rli.cc:
  replicate_same_server_id is now a member variable of RLI.
sql/rpl_rli.h:
  replicate_same_server_id is now a member variable of RLI.
sql/slave.cc:
  Using RLI-specific member variable replicate_same_server_id instead of
  global instance.
  Moving comments about skipping logic to exec_relay_log_event().
  Moving event execution logic to exec_relay_log_event().
sql/sql_binlog.cc:
  Using apply_event() directly and adding comment with explenation.