Debug: fixes for Nuttx.py debug gdb add-ons

also fixed preceding mask calculation in show heaps
Debug: fixes for gdb extension macros
mpu6000: allow disabling of on-sensor low pass filter

used for vibration testing
ets_airspeed: fixed to add differential_pressure_raw_pa

thanks to hxxnrx for this fix!
px_uploader: added ModemManager warning