Support the IBM i platform.
- add a new file src/unix/ibmi.c
- extract the common functions from /src/unix/aix.c into aix-common.c
- update uv.gyp and include/uv-unix.h to enable the new file ibmi.c
PR-URL: https://github.com/libuv/libuv/pull/1601
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>