MFC r318649:

The connect() system call should return -1 and set errno to EAFNOSUPPORT
if it is called on a TCP socket

• with an IPv6 address and the socket is bound to an IPv4-mapped IPv6 address.
• with an IPv4-mapped IPv6 address and the socket is bound to an IPv6 address.

Thanks to Jonathan T. Leighton for reporting this issue.

Reviewed by: bz, gnn
Differential Revision: https://reviews.freebsd.org/D9163