SYNOPSIS
	void walk_mapping(mapping m, string func, object ob, mixed extra)
	void walk_mapping(mapping m, closure cl, mixed extra)

DESCRIPTION
	Calls ob->func(key, value1, ..., valueN, extra) resp. applies
	the closure to every entry in the mapping. The keys are passed
	by value, the values are passed by reference and can be
	changed in the function.

SEE ALSO
	map_mapping(E), filter_mapping(E)