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).

Python/thread.c

@@ -95,6 +95,11 @@ PyThread_init_thread(void)
 	PyThread__init_thread();
 }
 
+/* Support for runtime thread stack size tuning.
+   A value of 0 means using the platform's default stack size
+   or the size specified by the THREAD_STACK_SIZE macro. */
+static size_t _pythread_stacksize = 0;
+
 #ifdef SGI_THREADS
 #include "thread_sgi.h"
 #endif
@@ -150,6 +155,28 @@ PyThread_init_thread(void)
 #endif
 */
 
+/* return the current thread stack size */
+size_t
+PyThread_get_stacksize(void)
+{
+	return _pythread_stacksize;
+}
+
+/* Only platforms defining a THREAD_SET_STACKSIZE() macro
+   in thread_<platform>.h support changing the stack size.
+   Return 0 if stack size is valid,
+          -1 if stack size value is invalid,
+          -2 if setting stack size is not supported. */
+int
+PyThread_set_stacksize(size_t size)
+{
+#if defined(THREAD_SET_STACKSIZE)
+	return THREAD_SET_STACKSIZE(size);
+#else
+	return -2;
+#endif
+}
+
 #ifndef Py_HAVE_NATIVE_TLS
 /* If the platform has not supplied a platform specific
    TLS implementation, provide our own.