bpo-18049: Sync thread stack size to main thread size on macOS (GH-14748)

This changeset increases the default size of the stack
for threads on macOS to the size of the stack
of the main thread and reenables the relevant
recursion test.
diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
index a36d16c..994e35b 100644
--- a/Python/thread_pthread.h
+++ b/Python/thread_pthread.h
@@ -40,7 +40,8 @@
  */
 #if defined(__APPLE__) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
 #undef  THREAD_STACK_SIZE
-#define THREAD_STACK_SIZE       0x500000
+/* Note: This matches the value of -Wl,-stack_size in configure.ac */
+#define THREAD_STACK_SIZE       0x1000000
 #endif
 #if defined(__FreeBSD__) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
 #undef  THREAD_STACK_SIZE