Get rid of some unused code.

Looks like some aborted attempt at abstraction, which is no longer used.

(cherry picked from commit 2e6b82ab8ec0cc63837759873e412831de5a1826)
Get rid of `special-dots-printing?'.

Asumu said that he doesn't know of any other clients of this parameter
besides my class code.

(cherry picked from commit 0eed0f6e0e493b190abc912981bab59644a3a760)
Add `type-output-sexpr-tweaker'.

Sounds like a bad name, but I don't have anything better.  It's not some
"current-...-print" thing since it works on the sexpr that is intended
to be pretty-printed.  So I went with the above.

(cherry picked from commit 3c98d086904409b9c49d710134415d718d6ca65e)
Random improvement.

The thing that caught my eye is the missing `#:cache-keys?' which should
really be there.  But not too important.

(cherry picked from commit eaa6f85054c5c404507e5c9cbab0d3e93f468370)
Fix printing of * in -> types

(cherry picked from commit 38af459049819ecac24de6b349440e6c589703f9)