[Flightgear-devel] Cleanup unused locals

[Chris F. <ch...@ij...>]

These patches clean up some set-but-unused locals which cause warnings on current GCC.
There should be no change in semantics.
Tested against c5eba72c758b92b9120c38ae101f4a4ab2044ff8 ('next' at time of writing)

-- Chris