Move fontlock.hs into examples/ folder
Add haskell-show.el to ELFILES variable
Remove auto-generated haskell-site-file.el from repository
Reimplement 'make dist' target for git repository
Embed auto-detected version into haskell-mode.el and dist-target

The current version as inferred by `git describe` is embedded into
`haskell-mode.elc` for in-place compiles and is statically embedded
into the generated `.tar.gz` (which then does not depend on `git
describe` anymore) by rewriting the distributed `Makefile` and
`haskell-mode.el` files.

This Makefile hack has been stolen from magit's
[Makefile](https://github.com/magit/magit/blob/master/Makefile)