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/Modules/_struct.c b/Modules/_struct.c
index eeccc17..c95c76f 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -1373,14 +1373,14 @@ prepare_s(PyStructObject *self)
 
     self->s_size = size;
     self->s_len = len;
-    codes = PyMem_MALLOC((ncodes + 1) * sizeof(formatcode));
+    codes = PyMem_Malloc((ncodes + 1) * sizeof(formatcode));
     if (codes == NULL) {
         PyErr_NoMemory();
         return -1;
     }
     /* Free any s_codes value left over from a previous initialization. */
     if (self->s_codes != NULL)
-        PyMem_FREE(self->s_codes);
+        PyMem_Free(self->s_codes);
     self->s_codes = codes;
 
     s = fmt;
@@ -1502,7 +1502,7 @@ s_dealloc(PyStructObject *s)
     if (s->weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *)s);
     if (s->s_codes != NULL) {
-        PyMem_FREE(s->s_codes);
+        PyMem_Free(s->s_codes);
     }
     Py_XDECREF(s->s_format);
     freefunc free_func = PyType_GetSlot(Py_TYPE(s), Py_tp_free);