Vladimir Marangozov's long-awaited malloc restructuring.
For more comments, read the patches@python.org archives.
For documentation read the comments in mymalloc.h and objimpl.h.

(This is not exactly what Vladimir posted to the patches list; I've
made a few changes, and Vladimir sent me a fix in private email for a
problem that only occurs in debug mode.  I'm also holding back on his
change to main.c, which seems unnecessary to me.)
diff --git a/Objects/rangeobject.c b/Objects/rangeobject.c
index c603ac9..807cf51 100644
--- a/Objects/rangeobject.c
+++ b/Objects/rangeobject.c
@@ -61,7 +61,7 @@
 range_dealloc(r)
 	rangeobject *r;
 {
-	PyMem_DEL(r);
+	PyObject_DEL(r);
 }
 
 static PyObject *