If --log-bin is set to a directory name with the trailing 'FN_LIBCHAR', 
which will be '/' on Unix like systems, and '\\' on Windows like systems. 
the basename of the binlog is empty so that the created files named 
'.000001' and '.index'. It is not expected. 
The same thing happened to --log-bin-index, --relay-log and 
--relay-log-index options.

To resolve the problem, in these cases the program should report an error 
and abort.


sql/mysqld.cc:
  Added a check for the value of the --log-bin and --log-bin-index arguments, 
  if it's a directory, reports an error and aborts.
sql/rpl_rli.cc:
  Added a check for the value of the --relay-log and --relay-log-index arguments, 
  if it's a directory, reports an error and aborts.