which makes it possible to run RENAME TABLE
  on old tables when upgrading from 5.0.
  TODO: A stored procedure to rename all tables and
  databases with old name format into new format,
  it will simplify upgrade.
sql_table.cc:
  Making old tables seen with "#mysql50#" prefix.
  Adding warning into .err log when an old name is found.
sql_show.cc:
  Skip non-directories before filename_to_tablename
  call, to avoid unnecessary warnings.
strfunc.cc:
  Adding "error" argument to strconvert()
mysql_priv.h:
  Adding "error" agrument to strconvert()