Solaris support for the attach (-p) option

Because of course Solaris has to use a different IPC method to everything else and Ruby has to rewrite their FFI library on every release. Untested but it looks like Java's BSD port (including OS X) uses the same UNIX socket mechanism as Linux, so this should cover everything but Windows.

Oh well. No more installing the full JDK just to get jstack and then shaking my fist because it refuses to run as root.