Move some utility functions into the cdsl package.

- is_power_of_two
- next_power_of_two

Make sure we run doctests on these functions.

lib/cretonne/meta/cdsl/test_package.py

@@ -0,0 +1,8 @@
+from __future__ import absolute_import
+import doctest
+import cdsl
+
+
+def load_tests(loader, tests, ignore):
+    tests.addTests(doctest.DocTestSuite(cdsl))
+    return tests