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/Python/thread_nt.h b/Python/thread_nt.h
index 4dc6d6c..67f5ed5 100644
--- a/Python/thread_nt.h
+++ b/Python/thread_nt.h
@@ -196,7 +196,7 @@
 	if (obj.done == NULL)
 		return -1;
 
-	rv = _beginthread(bootstrap, 0, &obj); /* use default stack size */
+	rv = _beginthread(bootstrap, _pythread_stacksize, &obj);
 	if (rv == (Py_uintptr_t)-1) {
 		/* I've seen errno == EAGAIN here, which means "there are
 		 * too many threads".
@@ -335,3 +335,30 @@
 	if (!(aLock && LeaveNonRecursiveMutex((PNRMUTEX) aLock)))
 		dprintf(("%ld: Could not PyThread_release_lock(%p) error: %l\n", PyThread_get_thread_ident(), aLock, GetLastError()));
 }
+
+/* minimum/maximum thread stack sizes supported */
+#define THREAD_MIN_STACKSIZE	0x8000		/* 32kB */
+#define THREAD_MAX_STACKSIZE	0x10000000	/* 256MB */
+
+/* set the thread stack size.
+ * Return 0 if size is valid, -1 otherwise.
+ */
+static int
+_pythread_nt_set_stacksize(size_t size)
+{
+	/* set to default */
+	if (size == 0) {
+		_pythread_stacksize = 0;
+		return 0;
+	}
+
+	/* valid range? */
+	if (size >= THREAD_MIN_STACKSIZE && size < THREAD_MAX_STACKSIZE) {
+		_pythread_stacksize = size;
+		return 0;
+	}
+
+	return -1;
+}
+
+#define THREAD_SET_STACKSIZE(x)	_pythread_nt_set_stacksize(x)