Added column number to FC for better error support/source tracking (corrected issue reference)

I have update the issue reference to the right one, sorry for the inconvenience. It should not close #508 when merged now.
> **NOTE:**
> I have changed Eq of FC to always return true, and made a newtype FC' for actual comparison. This is because many structures in the abstract syntax derive Eq and are dependent on FC equality, which is sometimes wrong. If there are disagreements about this change, please voice your opinions before merging.