Portable Python script across Python version

Make scripts more future-proof by importing most __future__ stuff.

Differential Revision: https://reviews.llvm.org/D55208

llvm-svn: 349504
diff --git a/clang/utils/ABITest/Enumeration.py b/clang/utils/ABITest/Enumeration.py
index 7606724..24f5b5f 100644
--- a/clang/utils/ABITest/Enumeration.py
+++ b/clang/utils/ABITest/Enumeration.py
@@ -1,6 +1,6 @@
 """Utilities for enumeration of finite and countably infinite sets.
 """
-from __future__ import print_function
+from __future__ import absolute_import, division, print_function
 ###
 # Countable iteration