+PH/18 Exim was not recognizing the "net-" search type prefix in match_ip lists
+ (Bugzilla #53).
+
+PH/19 Exim expands the IPv6 address given to -bh to its full non-abbreviated
+ canonical form (as documented). However, after a host name lookup from
+ the IP address, check_host() was doing a simple string comparison with
+ addresses acquired from the DNS when checking that the found name did
+ have the original IP as one of its addresses. Since any found IPv6
+ addresses are likely to be in abbreviated form, the comparison could
+ fail. Luckily, there already exists a function for doing the comparison
+ by converting both addresses to binary, so now that is used instead of
+ the text comparison.
+
+PH/20 There was another similar case to PH/19, when a complete host name was
+ given in a host list; looking up its IP address could give an abbreviated
+ form, whereas the current host's name might or might not be abbreviated.
+ The same fix has been applied.
+