uv: fix setsockopt for multicast options

Float patch to fix setsockopt for multicast on Solaris and derivatives.
Original commit message:

  solaris: fix setsockopt for multicast options

  On Solaris and derivatives such as SmartOS, the length of socket options
  for multicast and ttl options is not always sizeof(char).

  This fixes the udp_options and udp_options6 tests.

Ref: https://github.com/libuv/libuv/pull/243



Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
PR-URL: https://github.com/joyent/node/pull/9179