Include <unistd.h> in Python.h. Fixes #500924.
diff --git a/Python/thread.c b/Python/thread.c
index df42f31..f9a4de9 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -5,7 +5,7 @@
    which is included by this file dependent on config settings.
    Stuff shared by all thread_*.h files is collected here. */
 
-#include "pyconfig.h"
+#include "Python.h"
 
 /* pyconfig.h may or may not define DL_IMPORT */
 #ifndef DL_IMPORT	/* declarations for DLL import/export */
@@ -24,10 +24,6 @@
 #endif
 #endif
 
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
-#endif
-
 #ifdef __DGUX
 #define _USING_POSIX4A_DRAFT6
 #endif