ipv4 cidr prefix aggregator
takes a list of prefixes in conventional format on stdin, and performs two
optimisations to reduce the length of the prefix list. It removes any
supplied prefixes which are supurfluous because they are already included in
another supplied prefix (e.g., 203.97.2.0/24 would be removed if
203.97.0.0/17 was also supplied), and identifies adjacent prefixes that can
be combined under a single, shorter-length prefix (e.g., 203.97.2.0/24 and
203.97.3.0/24 can be combined into the single prefix 203.97.2.0/23).
