patch 8.0.1635: undefining _POSIX_THREADS causes problems with Python 3

Problem:    Undefining _POSIX_THREADS causes problems with Python 3. (Micah
            Bucy, closes #2748)
Solution:   Remove the lines.

Author: brammool

src/if_python3.c

@@ -34,11 +34,6 @@
 
 #include <limits.h>
 
-/* Python.h defines _POSIX_THREADS itself (if needed) */
-#ifdef _POSIX_THREADS
-# undef _POSIX_THREADS
-#endif
-
 #if defined(_WIN32) && defined(HAVE_FCNTL_H)
 # undef HAVE_FCNTL_H
 #endif

src/version.c

@@ -766,6 +766,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1635,
 /**/
     1634,
 /**/