+PH/03 When creating an mbox file for a virus/spam scan, use fseek() instead of
+ fread() to skip over the body file's header line, because in Cygwin the
+ header line is locked and is inaccessible.
+
+PH/04 Added $message_exim_id, ultimately to replace $message_id (they will both
+ co-exist for some time) to make it clear that it is the Exim ID that is
+ referenced, not the Message-ID: header line.
+