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/Python/pythonrun.c b/Python/pythonrun.c
index 49e616e..ee6ce07 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -543,7 +543,7 @@
 	if (n == NULL) {
 		if (err.error == E_EOF) {
 			if (err.text)
-				free(err.text);
+				PyMem_DEL(err.text);
 			return E_EOF;
 		}
 		err_input(&err);
@@ -1009,7 +1009,7 @@
 	v = Py_BuildValue("(ziiz)", err->filename,
 			    err->lineno, err->offset, err->text);
 	if (err->text != NULL) {
-		free(err->text);
+		PyMem_DEL(err->text);
 		err->text = NULL;
 	}
 	switch (err->error) {