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/Modules/mpzmodule.c b/Modules/mpzmodule.c
index e701d85..1aaf787 100644
--- a/Modules/mpzmodule.c
+++ b/Modules/mpzmodule.c
@@ -123,7 +123,7 @@
 #ifdef MPZ_DEBUG
 	fputs( "mpz_object() called...\n", stderr );
 #endif /* def MPZ_DEBUG */
-	mpzp = PyObject_NEW(mpzobject, &MPZtype);
+	mpzp = PyObject_New(mpzobject, &MPZtype);
 	if (mpzp == NULL)
 		return NULL;
 
@@ -285,7 +285,7 @@
 	fputs( "mpz_dealloc() called...\n", stderr );
 #endif /* def MPZ_DEBUG */
 	mpz_clear(&mpzp->mpz);
-	PyMem_DEL(mpzp);
+	PyObject_Del(mpzp);
 } /* mpz_dealloc() */