Fix #9600. Don't use relative imports for _multiprocessing on Windows.
Same fix as #9513 on 3.x.
diff --git a/Lib/multiprocessing/forking.py b/Lib/multiprocessing/forking.py
index 7eda991..cec184c 100644
--- a/Lib/multiprocessing/forking.py
+++ b/Lib/multiprocessing/forking.py
@@ -150,7 +150,7 @@
     import _subprocess
     import time
 
-    from ._multiprocessing import win32, Connection, PipeConnection
+    from _multiprocessing import win32, Connection, PipeConnection
     from .util import Finalize
 
     #try: