Implement tricky combinators from Text.Parsec.Combinator

[schneiderfelipe]

Or find alternatives:

• [x] anyToken
• [x] eof
• [x] notFollowedBy
• [ ] manyTill
• [ ] lookAhead

Code can be found here.

EDIT: ensure they are tested as well.

[schneiderfelipe]

notFollowedBy requires revision, as it still uses the old setPosition function. We have to come up with an alternative implementation that does not require arbitrary repositioning.

One solution might be marking the stream and asking it to go back to the mark (one new function to mark and another to go back). That might or might not be merged with the lastPosition idea, etc., but it might be worth generalizing.