Async-io and lost files, possible patch.

To those who have reported that async-io lost track of files during a
clean restart:

I have now found a likely source to this problem. See
http://hem.passagen.se/hno/squid/ for a patch file and report any
success or failures with this patch to squid-bugs@ircache.net.

The reason why I failed to repeat the problem earlier was that my test
system was to lightly loaded. The problem corrected only appears if disk
I/O is completely choked while writing the store index during shutdown.

---
Henrik Nordstrom
Spare time Squid hacker