MFC rev 1.203:

MFC rev 1.203:
  Fix IP_SENDSRCADDR semantics.

   * To use this option with a UDP socket, it must be bound to a local port,
     and INADDR_ANY, to disallow possible collisions with existing udp inpcbs
     bound to the same port on other interfaces at send time.

   * If the socket is bound to INADDR_ANY, specifying IP_SENDSRCADDR with
     INADDR_ANY will be rejected as it is ambiguous.

   * If the socket is bound to an address other than INADDR_ANY, specifying
     IP_SENDSRCADDR with INADDR_ANY will be disallowed by in_pcbbind_setup().

Reviewed by:	silence on -net
Tested with:	src/tools/regression/netinet/ipbroadcast