remove extension from binary log if the user specifies one to avoid
    non-rotatable logs
fixed possible use of unitialized IO_CACHE in debug mode


sql/log.cc:
  fixed race condition in automatic binlog rotation
sql/mysqld.cc:
  remove extension from binary log if the user specifies one to avoid
  non-rotatable logs
sql/slave.cc:
  fixed race condition with slave thread during server shutdown
sql/sql_class.h:
  new_file() needed an argument to know if it was called withing the 
  log mutex or not
sql/sql_repl.cc:
  fixed possible use of unitialized IO_CACHE in debug mode