surface: Erase a lot of unused codes in Aerial.cpp.

I've kept the codes for future reference, but recent several dozens of
commits proved that they are quite unlikely to be used again.
surface: Renamed Aerial::brk to brake and make it working again.

The old name was too cryptographic, that's why we changed it.
Also, spoiler is distinct concept from brake, so we make it work as
it should.
surface: Fix Aerial::animAI() sets destArrived flag unintentionally.

The bug made the waypoint list in the demo7.nut script to mulfunction.

Also tweaked aerial.nut for more accurate landing.
surface: Multiple A10's in demo7.nut.

Also fixed a bug that Aerial vehicles tries to attack allies.
surface: Add delta-time parameter to aerialLanding to time-integrate.

With this feature, autopilot accuracy would be improved by PID control.
The filter design is still poor, though.