The old way to store the length prefix was (256 - length); This is now changed to (length -249)
Fixed also that some defines to have a MARIA_ prefix

storage/maria/ma_control_file.c:
  Added comment
storage/maria/ma_key.c:
  Added MARIA_ prefix to some defines
  Changed how packed transid length was stored
storage/maria/ma_open.c:
  Added MARIA_ prefix to some defines
storage/maria/maria_def.h:
  Added MARIA_ prefix to some defines
  Changed how packed transid length was stored