Add MHD_OPTION_LISTENING_ADDRESS_REUSE option.

When specified with true value, allow listening address:port
reuse (mostly by using SO_REUSEPORT, or SO_REUSEADDR on Windows).

When specified with false value, disallow listening address:port
reuse (most no action, SO_EXCLUSIVEADDRUSE no Windows).

When not specified, use current behavior (SO_REUSEADDR everywhere).