This file accompanies the following files:

/complex/gateway.c
		Defines an object which will accept a list of exit names
		destination names and exit checks.  Essentially behaves 
		like a room but it is portable.  If you carry it and
		say one of the words it recognises then you are teleported!

/basic/openable.c
		Defines simple logic for things that can be opened or closed.

/sys/door_logic.h
		Defines return codes for monitoring calls to open / close.

/sys/door.h	Defines macros for building doors.
/obj/door.c	Defines a door as a gateway with an associated data structure
		which is shared with another gateway in another room.	

/obj/doordata.c
		The data structure which is shared between two gateways.
		It contains the open / closed flags and associated logic.

/sys/lock_logic.h
		Defines return codes for monitoring calls to unlock / lock.

/basic/lockable.c
		Defines simple logic for things that can be unlocked or locked.
/basic/lockdata.c
		The data structure which is shared between two lockable doors.
		It contains the unlock / lock flags and associated logic.

/obj/key.c	Defines a simple key object.
obj/key_lock.c	Defines a lock that works with keys.

obj/lockable_door.c
		A sub class of door that is also lockable.

/example/workroom.c
		A copy of my workroom, to show you how to use doors.
