SF #737473: Show up-to-date source code in tracebacks always.
And add an optional argument 'filename' to linecache.checkcache()
to enable checking caches per-file.
diff --git a/Misc/NEWS b/Misc/NEWS
index 6c0935e..59c3ef6 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -59,6 +59,9 @@
 
 - Bug #1017553: fix bug in tarfile.filemode()
 
+- Bug #737473: fix bug that old source code is shown in tracebacks even if
+  the source code is updated and reloaded.
+
 Build
 -----