Add synopsis and parameter cross-link support to Python domain

This adds a new `py:param` Sphinx role that can be used (in addition
to the `py:obj` role) to reference parameters.

docs/api.rst

@@ -63,6 +63,7 @@ The following options can be customized for each object type using
 
       - ``std`` (including object types added using :py:obj:`sphinx.application.Sphinx.add_object_type`)
       - ``c`` and ``cpp``
+      - ``py``
 
    .. admonition:: Example
       :class: example
@@ -88,6 +89,7 @@ The following options can be customized for each object type using
 
       - ``std`` (including object types added using :py:obj:`sphinx.application.Sphinx.add_object_type`)
       - ``c`` and ``cpp``
+      - ``py``
 
    .. admonition:: Example
       :class: example

docs/cpp.rst

@@ -34,10 +34,9 @@ C++ domain customization
 
 .. confval:: cpp_qualify_parameter_ids
 
-   :python:`bool` specifying whether function, template, and macro parameters
-   should be assigned fully-qualified ids (for cross-linking purposes) of the
-   form ``<parent-id>-p-<param-name>`` based on the id of the parent
-   declaration.  Defaults to :python:`True`.
+   Specifies whether function, template, and macro parameters should be assigned
+   fully-qualified ids (for cross-linking purposes) of the form
+   ``<parent-id>-p-<param-name>`` based on the id of the parent declaration.
 
    If set to :python:`False`, instead the shorter unqualified id
    ``p-<param-name>`` is used.  This option should only be set to

docs/python.rst

@@ -75,3 +75,13 @@ Python domain customization
 
       The concise syntax is non-standard and not accepted by Python type
       checkers.
+
+.. confval:: python_qualify_parameter_ids
+
+   Specifies whether function parameters should be assigned fully-qualified ids
+   (for cross-linking purposes) of the form ``<parent-id>.<param-name>`` based
+   on the id of the parent declaration.  Defaults to :python:`True`.
+
+   If set to :python:`False`, instead the shorter unqualified id
+   ``p-<param-name>`` is used.  This option should only be set to
+   :python:`False` if each Python declaration is on a separate page.