Correct two passive exceptions.
Correct two passive exceptions.

    Added `iste' to the exceptional verbs that gets an optional `n'
    before passive morpheme (`istenir' & `istenilir'),  and fixed
    exception regarding `koy'. Now, if final `y' is replaced with an
    `n', we allow passive morpheme to be completely dropped (`konur',
    `konulur' and `koyulur' are all accepted).

coltekin/TRmorph,coltekin/TRmorph,coltekin/TRmorph