changes.rst: name vmod function / constructor / method RST xref like VCL

Ref 904ceabf

doc/changes.rst

@@ -46,8 +46,8 @@ NEXT (2019-09-15)
 * Retired the ``BackendStart`` log tag - ``BackendOpen`` contains all
   the information from it
 
-C APIs (for vmod and utility authors)
--------------------------------------
+APIs / VMODs
+------------
 
 * ``WS_Reserve()`` is now deprecated and any use should trigger a
   compiler warning. It is to be replaced by
@@ -66,6 +66,26 @@ C APIs (for vmod and utility authors)
   We provide a script to help automate this change in the
   ``tools/coccinelle`` subdirectory of the source tree.
 
+* The RST references generated by ``vmodtool.py`` have been changed to
+  match better the VCL syntax to avoid overhead where references are
+  used. The new scheme for a vmod called *name* is:
+
+  * ``$Function``: *name*\ .\ *function*\ ()
+  * ``$Object`` constructor: *name*\ .\ *object*\ ()
+  * ``$Method``: x\ *object*\ .\ *method*\ ()
+
+  To illustrate, the old references::
+
+    :ref:`vmod_name.function`
+    :ref:`vmod_name.obj`
+    :ref:`vmod_name.obj.method`
+
+  now are renamed to::
+
+    :ref:`name.function()`
+    :ref:`name.obj()`
+    :ref:`xobj.method()`
+
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