Adding new variables with paths to where the binary log files
and the relay log files are located. Three new global read-only
variables are added and one has changed contents.

log_bin_basename
  This variable hold the full path and name used for the binary
  logs: not including the extension of the files.

log_bin_index
  This variable contain the full path to the binary log index
  file.

relay_log_basename
  This variable hold the full path and name used for the relay
  logs: not including the extension of the files.

relay_log_index
  This variable now contain the full path to the relay log
  index file.  Previously, it just contained the value supplied
  to mysqld option relay-log-index,  which was then used to
  compute the path to the index file.