Update bitwise_or op_range.

Update bitwise_or op_range.

If the LHS of a bitwise OR is positive, then so are both operands when
using op1_range or op2_range.

	gcc/
	* range-op.cc (operator_bitwise_or::op1_range): If LHS is signed
	positive, so are both operands.

	gcc/testsuite
	* g++.dg/cpp23/attr-assume-opt.C (f2b): Alternate flow test.