Implement pointer_or_operator.

The class pointer_or is no longer used, and can be removed.  Its
functionality was never moved to the new dispatch system.
This implements operator_bitwise_or::fold_range() for prange operands.

	* range-op-mixed.h (operator_bitwise_or::fold_range): Add prange
	variant.
	* range-op-ptr.cc (class pointer_or_operator): Remove.
	(pointer_or_operator::op1_range): Remove.
	(pointer_or_operator::op2_range): Remove.
	(pointer_or_operator::wi_fold): Remove.
	(operator_bitwise_or::fold_range): New prange variant.