illumos syscalls: fd handling (part 4)

illumos syscalls: fd handling (part 4)

Almost everything looked OK. Added a couple of POST_newFd_RES
macro uses.

There are a few functions that create fds other than via RES
(like pipe). For these I think that we need to add a
POST_newFd(fd) macro, plus in a few places refactor so that
RES is available to set the status after ML_(get_next_new_fd).