MFC r312105,r312162:

r312105:

Conditionalize libwrap support into inetd based on MK_TCP_WRAPPERS

This will allow inetd to stand by itself without libwrap.

Relnotes: yes

r312162:

Fix up r312105

- Only #include tcpd.h when LIBWRAP is true to avoid header include errors
- Only define whichaf when LIBWRAP is true to avoid -Wunused warning and
to avoid issues with structs being defined that should only be defined
when tcpd.h is included.

Pointyhat to: ngie

MFC: r298111 r298114

Directly set the O_CLOEXEC flags via the open(2) attributes
Use the SOCK_CLOEXEC flags in the socket(2) 'type' attribute instead of
calling fcntl(2)

Sponsored by: Essen Hackathon

MFC 281734-281736,287997-287998:

- Fix a crash on a rpc entry when an IPv6 address is explicitly
specified in -a flag.

- Fix a bug that sockaddr_in was used where sockaddr_in6 should have
been used. This was not actually harmful because offsetof(struct
sockaddr_in, sin_port) is equal to offsetof(struct sockaddr_in6,
sin6_port).

- Remove unused union p_un.

- Use NI_MAXHOST-long buffer for getnameinfo().
Although INET6_ADDRSTRLEN was designed to hold the longest
IPv6 address in IPv4-mapped address format a long time ago,
getnameinfo() can return scope identifier in addition to it.

MFC 281734-281736,287997-287998:

- Fix a crash on a rpc entry when an IPv6 address is explicitly
specified in -a flag.

- Fix a bug that sockaddr_in was used where sockaddr_in6 should have
been used. This was not actually harmful because offsetof(struct
sockaddr_in, sin_port) is equal to offsetof(struct sockaddr_in6,
sin6_port).

- Remove unused union p_un.

- Use NI_MAXHOST-long buffer for getnameinfo().
Although INET6_ADDRSTRLEN was designed to hold the longest
IPv6 address in IPv4-mapped address format a long time ago,
getnameinfo() can return scope identifier in addition to it.