I'm busy implementing the IEEE754 contexts for cdecimal. To keep things
in sync, it would be nice to agree how they should be created.


Suggestions:

1) c = Decimal64Context

2) c = Context(Decimal64)

3) ?


I have a preference for 2). It's clear that you get a new Object and
the user does not have to wonder if a template context will be
contaminated when using setcontext(Decimal64Context).

(I know there are measures against that, but setcontext( Context(Decimal64))
is explicit rather than implicit.)