Refit u_user_unlink for remote or local users, and for /KILL
Add (possibly incorrect) code for s2s KILL and QUIT
Add prefix parameter to u_trie_each to limit result.

This is useful for example with users_by_uid to get a list of users on a
given server, i.e. u_trie_each(users_by_uid, "22U", cb, NULL) will call
cb() for users on the server with SID 22U.
Reorganize u_server_unlink, delete users on unlinked server
Unlink servers recursively
Add /MAP implementation that probably works.
Keep link and user count for servers, display user count in /MAP
Make /MAP output look more like that of charybdis
Process SID messages (untested)
Short-circuit vsnf() as strlcpy when the format is exactly "%s"
Prepend "Quit: " to quit messages from users
Get rid of silly CTX_SBURST connection context.

To me, it looks like SBURST was only used to limit SVINFO to connecting
servers, and to detect end-of-burst in PONG. Other than that, it was
just extra garbage that was getting tedious to consider.
Support sending of numerics to remote users (maybe!)
Perform correct local/remote user test
Add and use IS_USER_LOCAL() macro
Add IS_SERVER_LOCAL() macro
Redo a bit of sendto logic, especially regarding flags
Change return type of command callbacks to `int'
4.3bsd has no `const', and fix stack corruption bug.

When depth is 0, p->indent[depth - {3,2}] writes outside the bounds
of the struct map_priv, which corrupts the u_user *u in m_map, causing
segfaults when sending RPL_MAPEND.