[3.8] bpo-38600: NULL -> ``NULL``. (GH-17001) (GH-17003)

Also fix some other formatting.
(cherry picked from commit e835b31d2b212c3c7820364398979cae2a9740b2)
diff --git a/Doc/c-api/init_config.rst b/Doc/c-api/init_config.rst
index 5e18300..6b16b5b 100644
--- a/Doc/c-api/init_config.rst
+++ b/Doc/c-api/init_config.rst
@@ -61,8 +61,8 @@
 
    List of ``wchar_t*`` strings.
 
-   If *length* is non-zero, *items* must be non-NULL and all strings must be
-   non-NULL.
+   If *length* is non-zero, *items* must be non-``NULL`` and all strings must be
+   non-``NULL``.
 
    Methods:
 
@@ -608,7 +608,7 @@
 
       :data:`sys.pycache_prefix`: ``.pyc`` cache prefix.
 
-      If NULL, :data:`sys.pycache_prefix` is set to ``None``.
+      If ``NULL``, :data:`sys.pycache_prefix` is set to ``None``.
 
    .. c:member:: int quiet