Patch #1454481:  Make thread stack size runtime tunable.

Heavily revised, comprising revisions:
46640 - original trunk revision (backed out in r46655)
46647 - markup fix (backed out in r46655)
46692:46918 merged from branch aimacintyre-sf1454481

branch tested on buildbots (Windows buildbots had problems
not related to these changes).
diff --git a/Misc/NEWS b/Misc/NEWS
index 04240e8..82838f3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -112,6 +112,9 @@
 - Patch #1435422: zlib's compress and decompress objects now have a
   copy() method.
 
+- Patch #1454481: thread stack size is now tunable at runtime for thread
+  enabled builds on Windows and systems with Posix threads support.
+
 - On Win32, os.listdir now supports arbitrarily-long Unicode path names
   (up to the system limit of 32K characters).