[Feature request] Allow expr * 0 to be constant 0

[Rangi42]

As of #1399, we allow expr && 0 and expr & 0 to be constant 0, and expr || non-0 to be constant 1.

expr * 0 should also be valid to allow as constant 0. I don't think there would be any issues with that, and it could be helpful with (cond * val1) + (!cond * val2) "ternaries".