remove mc_pos_control_tests since empty
move test_controlmath.cpp into systemcmds/tests directory

"internal compiler error: in trunc_int_for_mode, at explow.c:55"

More than a year ago I started the easy to use math::Functions to handle
the always used mathematical SISO functions to be tested and available.

I switched x, y and z stick input to the freesh programmed deadzone and
exponential functions from the library to unify and clarify their use.
I just realized yaw was left over because it lead to a drift problem in
certain new use cases.

Now I'm just adding the yaw stick to the already well working method.

bug in the navigator where this flag is not correctly set.

FlightTaskOffboard: ensure supported offboard setpoints