Name: file_name - get the filename of an object

Syntax:
	string file_name(object obj)

Description:
	The file_name efun gets the filename of an object. If the object is a
	cloned object, then it will not have any corresponding file name, but
	rather a new name based on the original file name.

	Each cloned object in the game has a number, this number is appended
	to the filename, if file_name is called with a cloned object as
	argument.

	Note: find_object(file_name(ob)) == ob is guaranteed to be true for
	      all objects ob.

Return value:
	A string containing the filename of the object.

Examples:
	file_name(this_player()) could return "obj/wizard#11305"

See also: efun/save_object, efun/restore_object, efun/write_file, efun/cat, efun/ed, efun/file_size, efun/file_date, lib/neat_file, lib/slash_neat_file, lib/real_file, efun/find_object