Apply fixes, remove duplicates.

Apply fixes to _random, cStringIO, errno, operator, sys, zlib, etc.; also,
remove duplicate 2.7/math.pyi, 2.7/marshal.pyi.

builtins/2.7/time.pyi

@@ -1,5 +1,5 @@
 """Stub file for the 'time' module."""
-# based on autogenerated stub from typeshed and https://docs.python.org/2/library/time.html
+# See https://docs.python.org/2/library/time.html
 
 from typing import NamedTuple, Tuple, Union