perm: add a new L permissions

When a client has the L permission on the node, it can make links
between the node even if the owner of the node can't see the other node.

src/tools/pw-dump.c

@@ -1427,6 +1427,7 @@ static void dump_objects(struct data *d)
 		{ "w", PW_PERM_W },
 		{ "x", PW_PERM_X },
 		{ "m", PW_PERM_M },
+		{ "l", PW_PERM_L },
 		{ NULL, },
 	};