Warning fixes v3

This fixes a series of warnings across the system. Please perform a careful code review, then merge at will.
Although the line is non-trivial, this here is a floating point safe != operator:

```
(fabsf(flow.ground_distance_m - sonar_prev) > FLT_EPSILON)
```
Only if flow.ground_distance_m == sonar_prev the result of the operation is <= FLT_EPSILON. So I didn't really change the logic, but just made it floating point safe.