as we transform the 3.23 Load_log_event into a 4.0 Create_file_log_event which is one
byte longer, we need to increment event_len. The bug was that we did not increment it,
so later in code the end 0 was not seen so there was for example a segfault in
strlen(fname) because fname was not 0-terminated.
Other problems remain in 3.23->4.0 replication of LOAD DATA INFILE but they are less serious:
Exec_master_log_pos and Relay_log_space are incorrect. I'll document them.
They are not fixable without significant code changes (if you fix those problems in 4.0,
you get assertion failures somewhere else etc), * which are already done in 5.0.0 *.


sql/slave.cc:
  In 3.23->4.0 replication of LOAD DATA INFILE:
  as we transform the 3.23 Load_log_event into a 4.0 Create_file_log_event which is one
  byte longer, we need to increment event_len.
  So we need to modify the event_len stored in the event.
  And we need to decrement event_len when we compute the offset in the master's binlog.