Picobit now has triplets, which can be used to implement

Picobit now has triplets, which can be used to implement
vectors. Actually, 3 implementations of vectors have been written. One
that makes linked lists of triplets, another that used Chris Okasaki's
random access lists (the O(1) list operations are useless here since
we are implementing vectors, which have fixed size) and a last one
that has simple complete binary trees (the code is actually uglier
than the r-a-lists, since we have to build the tree all at once (no
cheap "consing"), and we have to find the smallest size of tree that
fits, which uses an ugly binary search through powers of 2).

Will have to get rid of some of the least useful primitives to make
room for ior and xor, and maybe others.