Update blurb entry.

Author: nascheme

Misc/NEWS.d/next/Core and Builtins/2019-06-29-16-27-23.bpo-37448.QI5V97.rst

@@ -0,0 +1,12 @@
+Add a radix tree to track used obmalloc arenas. Use to replace the old
+implementation of address_in_range(). The radix tree approach makes it easy
+to increase pool sizes beyond the OS page size. Boosting the pool and arena
+size allows obmalloc to handle a significantly higher percentage of requests
+from its ultra-fast paths.
+
+It also has the advantage of eliminating the memory unsanitary behavior of
+the previous address_in_range(). The old address_in_range() was marked with
+the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and
+_Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.
+
+Co-authored-by: Tim Peters <[email protected]>