- Lots of documentation.

- Do not prune volume marked as append when needing a
  new Volume.
- Print a warning message in SD if a non-used Volume
  is specified and autolabel not turned on.
- Correct a bug in chksum.c concerning SHA1 signatures
  (an * should have been & when checking for a bit flag).
- Print File:Block for all label records in label.c -- concerns
  primarily bls when doing Job listings (-j).
- Correct is_volume_in_use() to return false if testing
  on the same device where the Volume is already mounted.
- Define a init_done flag in the SD that is set when the
  devices are initialized and make users connecting wait.
  This prevents useless connect failure warning messages.
- Do additional device locking in ask_op_to_mount_volume()
  to prevent race conditions with a user labeling a Volume
  or autolabeling.