keys_cleanup branch is "ready" to merge.

[Vasily Chekalkin]

Hello.

Originally I created keys_cleanup branch to work on idea described on 
KeysRefactor wiki page. Fortunately (or unfortunately) I found that this 
will not work in current shape. So I want to merge branch into trunk by 
Wednesday.

Work done so far:

1. Remove references to "slices" (anyone remember what they were?)
2. Remove KEY_iterator_FLAGS (We have proper iterators now).

-- 
Bacek.