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.)

Python/ceval.c

@@ -2558,7 +2558,8 @@ call_function(func, arg, kw)
 		class);
 	
 	Py_DECREF(arg);
-	PyMem_XDEL(k);
+	if (k != NULL)
+		PyMem_DEL(k);
 	
 	return result;
 }