bpo-36540: Documentation for PEP570 - Python positional only arguments (#13202)

* bpo-36540: Documentation for PEP570 - Python positional only arguments

* fixup! bpo-36540: Documentation for PEP570 - Python positional only arguments

* Update reference for compound statements

* Apply suggestions from Carol

Co-Authored-By: Carol Willing <carolcode@willingconsulting.com>

* Update Doc/tutorial/controlflow.rst

Co-Authored-By: Carol Willing <carolcode@willingconsulting.com>

* Add extra bullet point and minor edits
diff --git a/Doc/c-api/code.rst b/Doc/c-api/code.rst
index fd3f691..e2b0b23 100644
--- a/Doc/c-api/code.rst
+++ b/Doc/c-api/code.rst
@@ -33,7 +33,7 @@
 
    Return the number of free variables in *co*.
 
-.. c:function:: PyCodeObject* PyCode_New(int argcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *lnotab)
+.. c:function:: PyCodeObject* PyCode_New(int argcount, int posonlyargcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *lnotab)
 
    Return a new code object.  If you need a dummy code object to
    create a frame, use :c:func:`PyCode_NewEmpty` instead.  Calling