Replace PF_* constants with AF_*

Replace PF_* constants with AF_*

AF_* constants appear to be more standardized, and in practice there's
always a one to one relationship between AF_* and PF_*, so let's
use AF_* instead of PF_*.

* xlat/domains.in: Remove.
* net.c: Do not define PF_UNSPEC.  Stop including "xlat/domains.h".
Replace PF_* with AF_*.  Replace domains with addrfams.
* tests/inet-cmsg.c: Replace PF_INET with AF_INET.
* tests/net-yy-inet.c: Likewise.
* tests/netlink_inet_diag.c: Likewise.
* tests/net-accept-connect.c: Replace PF_LOCAL with AF_LOCAL.
* tests/net-y-unix.c: Likewise.
* tests/net-yy-unix.c: Likewise.
* tests/netlink_unix_diag.c: Likewise.
* tests/net.expected: Replace PF_ with AF_.