document the performance fix to builtin_sum().

diff --git a/Misc/NEWS b/Misc/NEWS
index 7b010f1eadbb0c91d92ae556e3164f214e21fda9..0fd01965015355f2eb1b5642e6ddb382e44ff986 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -15,6 +15,9 @@ Core and builtins
 - Patch #820195: object.__contains__() now returns True or False instead
   of 1 or 0.
 
+- builtin_sum() now uses PyNumber_InPlaceAdd, fixing a previous
+  performance bug for sum(list_of_lists) and similar cases.
+
 Extension modules
 -----------------