Fix Solaris (SmartOS) build

  * On Solaris `fd_set` is defined in `sys/select.h`.
  * `libsocket`, `libnsl` and `libresolv` are required.

This makes it build cleanly if `MINIUPNPC_SET_SOCKET_TIMEOUT` is forced
to `false` (as tested on Joyent's SmartOS).
Merge pull request #34 from mmalecki/solaris

Fix Solaris (SmartOS) build