Revert backwards-incompatible const changes.
diff --git a/Include/modsupport.h b/Include/modsupport.h
index fc9f2e8..a56d07c 100644
--- a/Include/modsupport.h
+++ b/Include/modsupport.h
@@ -24,14 +24,14 @@
 PyAPI_FUNC(int) PyArg_Parse(PyObject *, const char *, ...);
 PyAPI_FUNC(int) PyArg_ParseTuple(PyObject *, const char *, ...);
 PyAPI_FUNC(int) PyArg_ParseTupleAndKeywords(PyObject *, PyObject *,
-                                                  const char *, const char **, ...);
+                                                  const char *, char **, ...);
 PyAPI_FUNC(int) PyArg_UnpackTuple(PyObject *, const char *, int, int, ...);
 PyAPI_FUNC(PyObject *) Py_BuildValue(const char *, ...);
 PyAPI_FUNC(int) _PyArg_NoKeywords(const char *funcname, PyObject *kw);
 
 PyAPI_FUNC(int) PyArg_VaParse(PyObject *, const char *, va_list);
 PyAPI_FUNC(int) PyArg_VaParseTupleAndKeywords(PyObject *, PyObject *,
-                                                  const char *, const char **, va_list);
+                                                  const char *, char **, va_list);
 PyAPI_FUNC(PyObject *) Py_VaBuildValue(const char *, va_list);
 
 PyAPI_FUNC(int) PyModule_AddObject(PyObject *, const char *, PyObject *);
diff --git a/Include/object.h b/Include/object.h
index 33b75be..9c91373 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -144,12 +144,12 @@
 typedef int (*getreadbufferproc)(PyObject *, int, void **);
 typedef int (*getwritebufferproc)(PyObject *, int, void **);
 typedef int (*getsegcountproc)(PyObject *, int *);
-typedef int (*getcharbufferproc)(PyObject *, int, const char **);
+typedef int (*getcharbufferproc)(PyObject *, int, char **);
 /* ssize_t-based buffer interface */
 typedef Py_ssize_t (*readbufferproc)(PyObject *, Py_ssize_t, void **);
 typedef Py_ssize_t (*writebufferproc)(PyObject *, Py_ssize_t, void **);
 typedef Py_ssize_t (*segcountproc)(PyObject *, Py_ssize_t *);
-typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, const char **);
+typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, char **);
 
 typedef int (*objobjproc)(PyObject *, PyObject *);
 typedef int (*visitproc)(PyObject *, void *);
@@ -239,9 +239,9 @@
 typedef void (*freefunc)(void *);
 typedef void (*destructor)(PyObject *);
 typedef int (*printfunc)(PyObject *, FILE *, int);
-typedef PyObject *(*getattrfunc)(PyObject *, const char *);
+typedef PyObject *(*getattrfunc)(PyObject *, char *);
 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
-typedef int (*setattrfunc)(PyObject *, const char *, PyObject *);
+typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 typedef int (*cmpfunc)(PyObject *, PyObject *);
 typedef PyObject *(*reprfunc)(PyObject *);