* raimo/inherit-listen-options/OTP-15824:
  The linger option is not transferred on *BSD

Removed unnecessary spec's causing dialyzer warnings.

Invalid guard tests for function sendto. It handled the,
invalid, socket address 'null'. Presumably, this was
intended for connected UDP sockets. Though, for a
connected (UDP) socket, the send function shall be used.

Its now possible to bind a socket to the (limited) broadcast
address by specifying 'broadcast' as address:

   socket:bind(Socket, broadcast)

This is *only* valid for family 'inet'.

Add testing of sending (broadcasting) to both "limited" broadcast address
and "subnet-directed" broadcast address.

OTP-15904

Add test case for the socket option acceptconn. Also make
minor correction (error when trying to set this option
was incorrect). Doc was also incorrect (spelled wrong).

OTP-15904

The nif code expects the socket address to be "complete",
that is all fields must exist. This was not the case for
a couple of functions, sendto, sendmsg and connect.
What was mssing was a call to 'ensure_sockaddr'.

Test: 1) Add a condition function to test if IPv6 is available
         and works.
      2) Needed to adjust a test case (actually a common function
         used in several test cases) since the socket address
	 data type has two optional fields, which we do not
	 initiate (when sending), but the nif-code does fill in.

OTP-15897