Add a version tag to the decimal module.

Lib/decimal.py

@@ -134,6 +134,8 @@ __all__ = [
     'setcontext', 'getcontext', 'localcontext'
 ]
 
+__version__ = '1.68'    # Highest version of the spec this complies with
+
 import copy as _copy
 import math as _math
 import numbers as _numbers