Set nonzero bits for multiplication and divisions by a power of 2.

Set nonzero bits for multiplication and divisions by a power of 2.

We're missing a lot of TLC in keeping track of nonzero bits across
range-ops.  It isn't an oversight, but just limited amount of hours to
implement stuff.

This patch keeps better track of the nonzero mask (really
maybe_nonzero bits as discussed) across multiplication and division
when the RHS is a power of 2.

It fixes PR107342 and also touches on PR55157.  In the latter, the
nonzero mask is being set quite late (CCP2) but could be set by evrp
time if we enhanced range-ops.  I have added tests from both PRs.

Tested

	PR tree-optimization/107342

gcc/ChangeLog:

	* range-op.cc (operator_mult::fold_range): New.
	(operator_div::fold_range): New.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/vrp122.c: New test.
	* gcc.dg/tree-ssa/vrp123.c: New test.