Fix Windows build
impl/tcpsocket: Don't try to listen() if not connected
core/types: Don't use MinGW 4.8.1 hack
boot/autodetect: Don't autodetect paths that are explicitly set in configuration
boot/autodetect: Automatic compiler path detection
util/windows: Drop launch scripts; they will not be needed anymore
interface/process: get_environment_variable() and ExecOptions
server/rccpp: Workaround different PATH handling in Wine
boot/autodetect: Allow detecting root to be empty string