Really fix accepting connections from "long" IPv6 address

Really fix accepting connections from "long" IPv6 address

Commit ee01ac19 (v4.3.23) enlarged player member hostaddr from 32 to
46 characters, but missed natstr member nat_hostaddr.  player_main()
copies hostaddr to nat_hostaddr.  Can overrun the destination, but
fortunately just into nat_hostname.

Impact:

* Can makes praddr() print only a suffix of the address.  Used by play
  command, for player messages during login and logout, and for
  logging.

* Can make player_main()'s test for "same address as last time" fail,
  causing extra "Last connection" messages.

* Matching against econfig key privip is not affected.

* Journal event login is not affected.