FlightGear - Flight Simulator FGAddon

This is the 2nd patch 'flightgear-fgaddon_path_fix2_Aircraft.patch' attached to
the thread at https://sourceforge.net/p/flightgear/mailman/message/33744249/ .

Due to the spinning out of the aircraft from FGData into the new FGAddon
repository, a number of aircraft now either do not work or have missing features
due to now incorrect file path assumptions. This fixes the incorrect references
to the Aircraft/ path for the aircraft 737-300, Concorde, fokker100, and
SenecaII.