Add In2Int, Long2Long, etc maps

[egg82]

Wouldn't increase the size much, and there's good utility in those maps anyway.

Slightly related, we might want to consider adding Int2Long, Bool2Double, (whatever) etc maps in new modules so people can pull/use those as well, although I'm not sure how best to do that without adding a hundred more modules or making a mess of things. Those other maps are useful, but yeah..