info_slave doesn't terminate on mush crash

Replying to Alan Schwartz <dunemush@pennmush.org>:

{{{ When M*U*S*H crashes, it looks like info_slave, which now uses unix sockets, doesn't terminate/die like it used to. As a result, you can't autorestart the mush because port 4201 is still being bound by the lingering info_slave. }}}

info_slave has used unix sockets instead of ip ones for years. It's just using datagrams instead of streams now. And, hmm... I can see how that might not cause a read error, even if the datagram socket is connected. I'll figure out a fix. Maybe wake up every few minutes and check to see if the mush's pid is still running.

However, when info_slave is started, almost all open file descriptors are explicitly closed (Except for stderr and the one used to talk to netmud.) See info_master.c:make_info_slave(). You thus shouldn't be getting errors about a port already in use because of an info_slave that is still running. I just checked with lsof, and the only things info_slave has open are libraries, netmush.log, and the socketpair pipe.

Okay, got a fix. But right now it only works on BSD systems with the kqueue()/kevent() polling interface (Which lets you wait for events as diverse as data waiting to be read from a socket and a process exiting). I'll whip up something using select() and period checks to see if a process exists for OSes without it, then commit.