Code review comment for lp://qastaging/~mir-team/mir/relative-pointer-events

<copy of review from before resubmission>

some of the x/y coords like:
32 + float x_axis_value, float y_axis_value,
could make use of some of the mir::geometry stuff, but probably more in line with the existing code's style to have them as floats.

229 + mir_pointer_event_axis_value(pev,mir_pointer_axis_vscroll),
space after comma

323 + const float dx = 7.0f;
324 + const float dy = 9.3f;
const ordering

suppose the last two are hygenic/nits, and the first is a minor suggestion for improvement, so approve overall