Resolve IPs to hostnames in web server logs

 This script is a drop-in replacement for the logresolve.pl
 script distributed with the Apache web server.
 .
 ip2host has the same basic design of forking children to handle
 the DNS resolution in parallel, but multiplexes the communication
 to minimize the impact of slow responses. This results in a
 significant speed improvement (approximately 10x faster), and
 the performance degrades more gracefully as the DNS timeout value
 is increased.