Reduce compiler warnings for example tests
Reduce compiler warnings for example tests

This removes compiler warnings for all the example tests without
actually modifying them from the version shown in the README.

blochberger/swift-sodium,opfeffer/swift-sodium,ziogaschr/swift-sodium,jedisct1/swift-sodium,opfeffer/swift-sodium,ziogaschr/swift-sodium,ziogaschr/swift-sodium,opfeffer/swift-sodium,jedisct1/swift-sodium,blochberger/swift-sodium,jedisct1/swift-sodium,opfeffer/swift-sodium,blochberger/swift-sodium,blochberger/swift-sodium,ziogaschr/swift-sodium