SE-0225: Adding isEven, isOdd, isMultiple to BinaryInteger

[Tino]

@Nevin

So… if we can get a better remainder function, then the current proposal is superfluous.

The will be a proposal for mod in the near future:

'Double modulo' operator

We should not be designing standard library interfaces around what's fastest to do in hardware. This is what C did (if we read "in hardware" as "on a Digital PDP" for some older features and possibly "on x86" for some more recent things), and we're all worse off for it. We should ensure that it is possible to take advantage of hardware fast paths where appropriate, and that we have a sound rationale when we diverge from common practice, but the design goal for the standard library cannot be "ma…

I'm not sure wether this would make SE-0225 superfluous, but imho mod is definitely more important and makes it trivial to implement isOdd correctly.