+JH/11 Add dnsdb tlsa lookup. From Todd Lyons.
+
+JH/12 Expand items in router/transport headers_add or headers_remove lists
+ individually rather than the list as a whole. Bug 1452.
+
+ Required for reasonable handling of multiple headers_ options when
+ they may be empty; requires that headers_remove items with embedded
+ colons must have them doubled (or the list-separator changed).
+