Add IPv6 support to rshd test/debug code:

Add IPv6 support to rshd test/debug code:

* compat_recv.c: Include sys/select.h and port-sockets.h.
(krb5_compat_recvauth_version): Only attempt krb4 authentication if the source
address is an IPv4 one.
(accept_a_connection): New function, derived from old krshd.c.  Listen on IPv6
as well as IPv4, if possible.
* krshd.c (main): Call accept_a_connection.  Change fromlen to a socklen_t.
(doit): Initialize s.  Change length passed to getsockname to a socklen_t.
(recvauth): Change len to socklen_t.  Cast peer IPv4 address before calling
krb5_compat_recvauth_version.
* defines.h: Include port-sockets.h.
(accept_a_connection): Declare.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@15075 dc483132-0cff-0310-8789-dd5450dbe970