Merge branch 'cλash' of http://git.stderr.nl/matthijs/projects/master-project

* 'cλash' of http://git.stderr.nl/matthijs/projects/master-project:
  Add lambdasimpl normalization pass.
  Make letremoveunused work for non-recursive lets.
  Let casesimpl generate non-recursive lets.
  Add mkNonRecLets and use it.
  Make letmerge work with non-recursive lets.
  Limit flattenLets to non-recursive lets only.
  Move flattenLets from Normalize to CoreTools.
  Make inlinebind work for non-recursive lets.
  Add empty let removal normalization pass.
  Rename letremove to letremovesimple.
  Don't try to simplify nested lets.
  Make letflat work with non-recursive lets.
  Make letsimpl work on and generate a non-recursive let.
  No longer add a top level let before normalization.
  Make some normalizations generate nonrecursive lets.
  Turn let recursification into its opposite.