use floor and ceil to ensure int bounds

[Wout4]

Bound calculations are not guaranteed to give integers, so convert before making an intvar

[Dimosts]

Which bugs does this tackle? I also saw the same thing in PR #454, so I guess you encountered, but I am not sure which get_bounds can return non ints.

[Wout4]

writing a constraint like x > 0.6 * y will get flattened to x > IV and IV == 0.6 * y.
We now get an error when creating IV, because it's precise bounds are float.

[Wout4]

We decided before that it's better to leave the bound calculations exact, so they are not guaranteed to return integers.
For now this example will crash ortools anyway, but better to fix it on our side ofcourse (and with #454 you can indeed make it work on ortools)

[tias]

One more thing; can you check whether it is non-integer, and in that case throw a warning? or is that excessive?

[Wout4]

I don't think there will ever be a surprise float appearing without the user writing it? Maybe a warning that we only have intvars and not realvars makes sense