2002-12-09	added list_empty() and hash_empty() functions

2002-09-12	fixed list_iterate function to return -1 if it gets
		an invalid argument

		include <config.h> and <compat.h> from source files, not
		from header file, since header file is sometimes
		installed as part of a user-visible API
		(those APIs should eventually be redesigned without the
		listhash code being publicly visible, but for now we
		need to accomodate this)

2002-07-07	modified list iterate function to return int
		(returns -1 if plugin function returns -1)