Python 3 compat.

Try to keep our Python sources compatible with both Python 2.7 and 3.

Check with 'pylint --py3k' and 'python -3'.

meta/cretonne/types.py

@@ -1,7 +1,7 @@
 """
 The cretonne.types module predefines all the Cretonne scalar types.
 """
-
+from __future__ import absolute_import
 from . import ScalarType, IntType, FloatType, BoolType
 
 #: Boolean.