Document the new stats (setsz and nodesz).

README.rst

@@ -859,8 +859,15 @@ The VMOD currently provides the following statistics:
 * ``elements``: the number of elements in the set (added via
   ``.add()``)
 
+* ``setsz``: the total size of the strings in the set -- the sum of
+  the lengths of all of the strings, including their terminating null
+  bytes
+
 * ``nodes``: the total number of nodes in the internal data structure
 
+* ``nodesz``: the size of a node in the internal data structure
+  (bytes)
+
 * ``leaves``: the number of leaf nodes in the internal data structure.
   There may be fewer leaf nodes than elements of the set, if the set
   contains common prefixes.

src/vmod_selector.vcc

@@ -759,8 +759,15 @@ The VMOD currently provides the following statistics:
 * ``elements``: the number of elements in the set (added via
   ``.add()``)
 
+* ``setsz``: the total size of the strings in the set -- the sum of
+  the lengths of all of the strings, including their terminating null
+  bytes
+
 * ``nodes``: the total number of nodes in the internal data structure
 
+* ``nodesz``: the size of a node in the internal data structure
+  (bytes)
+
 * ``leaves``: the number of leaf nodes in the internal data structure.
   There may be fewer leaf nodes than elements of the set, if the set
   contains common prefixes.