Merge in changes from fps head. Highlights:

Merge in changes from fps head. Highlights:

    Wed May 24 15:49:38 EST 2006  sjanssen@cse.unl.edu
      * instance Monoid ByteString

    Wed May 24 15:04:04 EST 2006  Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
      * Rearange export lists for the .Char8 modules

    Wed May 24 14:59:56 EST 2006  Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
      * Implement mapAccumL and reimplement mapIndexed using loopU

    Wed May 24 14:47:32 EST 2006  Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
      * Change the implementation of the unfoldr(N) functions.
      Use a more compact implementation for unfoldrN and change it's behaviour
      to only return Just in the case that it actually 'overflowed' the N, so
      the boundary case of unfolding exactly N gives Nothing.
      Implement unfoldr and Lazy.unfoldr in terms of unfoldrN. Use fibonacci
      growth for the chunk size in unfoldr

    Wed May 24 08:32:29 EST 2006  sjanssen@cse.unl.edu
      * Add unfoldr to ByteString and .Char8
      A preliminary implementation of unfoldr.

    Wed May 24 01:39:41 EST 2006  Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
      * Reorder the export lists to better match the Data.List api

    Tue May 23 14:04:32 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
      * pack{Byte,Char} -> singleton. As per fptools convention

    Tue May 23 14:00:51 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
      * elemIndexLast -> elemIndexEnd

    Tue May 23 13:57:34 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
      * In the search for a more orthogonal api, we kill breakFirst/breakLast,
        which were of dubious value

    Tue May 23 12:24:09 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
      * Abolish elems. It's name implied it was unpack, but its type didn't. it made no sense

    Tue May 23 10:42:09 EST 2006  Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
      * Minor doc tidyup. Use haddock markup better.

    Tue May 23 11:00:31 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
      * Simplify the join() implementation. Spotted by Duncan.