Some changes and bugfixes to delayed doors

The following change is effective starting from the next reboot:

- If a delayed door is blocked, you will no longer attempt to open it despite
  the block.

The following changes are effective now:

- A number of delayed doors in Moria are now gone. (Sometime in the future 
  they may be restored when the behaviour of hunting mobiles around them is 
  more robust.)

- The mudlled entrance leading into the mines of the dwarven overseer and his
  miners can no longer be blocked.