Fix extras/trailed_update/samples/vqueens.m.

extras/trailed_update/samples/vqueens.m:
	Use higher-order any insts to avoid the mode error in this module.

extras/trailed_update/var.m:
	Add extras modes to the freeze predicates that take closures with inst
	any.  (XXX This module could do with a re-write since Mercury now
	implements many of the features that had to be hacked around when
	it was written.)