Adding sunos.c for solaris/illumos support.

I added preliminary solaris/illumos support with event ports in `sunos.c` as mentioned in #112.  The other changes outside `sunos.c` were related to portability issues between BSD/Linux and SunOS.

This branch was tested with `make bench` on the following platforms:

* SmartOS joyent_20130629T040542Z with GCC 4.7.2
* CentOS+OpenVZ 2.6.32-042stab076.7 with GCC 4.7.1
* OS X 10.8.4 with clang 4.2

Here's the related documentation for event ports:

* [port_create(3c)](http://illumos.org/man/3c/port_create)
* [port_associate(3c)](http://illumos.org/man/3c/port_associate)
* [port_getn(3c)](http://illumos.org/man/3c/port_getn)
* [poll(2)](http://illumos.org/man/2/poll)