Use `setproctitle()` in `FreeBSD` as in the other `BSD` flavours.
Move `uv_setup_args()`, `uv_set_process_title()` and `uv_get_process_title()` to
`bsd-proctitle.c` so it's used by the supported BSDs.
PR-URL: https://github.com/libuv/libuv/pull/2042
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
