Currently, if one tries to bind a socket using INADDR_LOOPBACK inside a
jail, it will fail because prison_ip() does not take this possibility
into account.  On the other hand, when one tries to connect(), for
example, to localhost, prison_remote_ip() will silently convert
INADDR_LOOPBACK to the jail's IP address.  Therefore, it is desirable to
make bind() to do this implicit conversion as well.

Apart from this, the patch also replaces 0x7f000001 in
prison_remote_ip() to a more correct INADDR_LOOPBACK.