bpo-42519: Replace PyMem_MALLOC() with PyMem_Malloc() (GH-23586)

No longer use deprecated aliases to functions:

* Replace PyMem_MALLOC() with PyMem_Malloc()
* Replace PyMem_REALLOC() with PyMem_Realloc()
* Replace PyMem_FREE() with PyMem_Free()
* Replace PyMem_Del() with PyMem_Free()
* Replace PyMem_DEL() with PyMem_Free()

Modify also the PyMem_DEL() macro to use directly PyMem_Free().
diff --git a/Objects/stringlib/join.h b/Objects/stringlib/join.h
index 53bcbde..62e4c98 100644
--- a/Objects/stringlib/join.h
+++ b/Objects/stringlib/join.h
@@ -155,7 +155,7 @@ STRINGLIB(bytes_join)(PyObject *sep, PyObject *iterable)
     for (i = 0; i < nbufs; i++)
         PyBuffer_Release(&buffers[i]);
     if (buffers != static_buffers)
-        PyMem_FREE(buffers);
+        PyMem_Free(buffers);
     return res;
 }