bpo-18049: Define THREAD_STACK_SIZE for AIX to pass default recursion limit test (GH-15081)

* Define THREAD_STACK_SIZE for AIX to pass default recursion limit test

Author: aixtools

Misc/NEWS.d/next/Library/2019-08-02-16-44-42.bpo-18049.OA4qBL.rst

@@ -0,0 +1,3 @@
+Add definition of THREAD_STACK_SIZE for AIX in Python/thread_pthread.h
+The default thread stacksize caused crashes with the default recursion limit
+Patch by M Felt

Python/thread_pthread.h

@@ -47,6 +47,10 @@
 #undef THREAD_STACK_SIZE
 #define THREAD_STACK_SIZE 0x400000
 #endif
+#if defined(_AIX) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
+#undef THREAD_STACK_SIZE
+#define THREAD_STACK_SIZE 0x200000
+#endif
 /* for safety, ensure a viable minimum stacksize */
 #define THREAD_STACK_MIN 0x8000 /* 32 KiB */
 #else /* !_POSIX_THREAD_ATTR_STACKSIZE */