Fixed avwrapper exit calls, fixing issue #752

Try to keep old weapon sets (not tested at all)

Fixed fPIC link failure with arm and sparc architectures, fixing issue #757 Added TargetArch.cmake, from https://github.com/petroules/solar-cmake/blob/master/TargetArch.cmake

Don't set gravity to normal immediately on turn end, let watchdog do its job if game gets frozen