Raise the timeout in test_multiprocessing_* for slow buildbots (GH-12489)

Lib/test/_test_multiprocessing.py

@@ -70,7 +70,7 @@ except ImportError:
 #
 
 # Timeout to wait until a process completes
-TIMEOUT = 30.0 # seconds
+TIMEOUT = 60.0 # seconds
 
 def latin(s):
     return s.encode('latin')