Check if UseLoopBack socket option is supported
Check if UseLoopBack socket option is supported

Not all systems support the UseLoopBack socket option.
Network.Socket.setSocketOption throws an exception when a system doesn't
support the socket option. This commit checks if the system supports
`UseLoopBack` before attempting to set it.

commercialhaskell/intero,commercialhaskell/intero,chrisdone/intero,commercialhaskell/intero,chrisdone/ghci-ng,chrisdone/ghci-ng,chrisdone/intero,chrisdone/intero