Update TODO

TODO

-* Compatibility with earlier Varnish versions
+* associate with more data types
+  * ACL?
+  * BLOB?
+  * BOOL
+  * BYTES?
+  * DURATION
+  * HEADER, HTTP?
+  * IP?
+  * REAL
+  * STEVEDORE?
+  * TIME?
 
-* packaging
-
-* Test error handling for out-of-workspace conditions.
-
-* method .backref()
-
-* expose pcre limit params for regexen?
-  * not needed when we're using VRT_VRE_*
+* extend "secondary regex" support
+  * method .backref()
+  * caseless match option
+  * expose pcre limit params for regexen?
+For all of these, we'd have to use VRE_* rather than VRT_VRE_*
 
 * search algorithm for .matched() ?
   * See the XXX comment in the code.