bpo-38600: NULL -> ``NULL``. (GH-17001)
Also fix some other formatting.
diff --git a/Doc/c-api/marshal.rst b/Doc/c-api/marshal.rst
index 2f58043..7b179e2 100644
--- a/Doc/c-api/marshal.rst
+++ b/Doc/c-api/marshal.rst
@@ -16,7 +16,7 @@
The module supports two versions of the data format: version 0 is the
historical version, version 1 shares interned strings in the file, and upon
unmarshalling. Version 2 uses a binary format for floating point numbers.
-*Py_MARSHAL_VERSION* indicates the current file format (currently 2).
+``Py_MARSHAL_VERSION`` indicates the current file format (currently 2).
.. c:function:: void PyMarshal_WriteLongToFile(long value, FILE *file, int version)