How to handle floating point comparison warnings (DO NOT MERGE)

There are quite a few of these. I've looked at most of them and they are legitimate == 0.0 comparisons when the float was directly set to 0.0. One way to handle them is to turn off -Wno-float-equal. Another is using the mechanism in this pull (or something similar). Looking for comments on what direction to head.
Change this to <0.5 for arm and >0.5 for arm? If so, we should change the mavlink spec as well. Old code should continue to work.