Efun:	exec - connect a socket to a new object

Synopsis:
	int exec(object new, object old)

Description:
	This function is used to shift an interactive user between two
	objects. The function 'valid_exec' is called in '/secure/master.c'
	with the calling object as argument. If 'valid_exec' accepts
	the calling object the interactive user is switched from the object
	'old' to 'new'.

	It is very easy to become confused when writing the code that uses
	this efun. All the internal variables like 'this_player' or
	'this_object' remain unchanged, it is just the user that is 
	switched between the objects.

	This is one of the greater threats to security in the system. Unless
	the use is this efun is rigorously restricted anyone can become arch
	or keeper.

	Don't do this unless you're damn certain you what you are doing.

Return value:
	1, if successful, 0 if not

See also: efun/remove_interactive