Moving BigFloat to stdlib?

Unfortunately, we need big ints and big floats in the array hashing code to compute the difference between two subsequent elements in an array without any overflow or precision loss. That’s not great, but so far we haven’t found any other solution (see this PR). This system could be easily disabled via a build option, and hashing of ranges would then be O(N) instead of O(1), but by default I’m afraid we’ll have to keep the types in Base. Though we can avoid exporting them from Base and use a stdlib module for that instead.