Identifiers with double primes are parsed as character literals in Haskell

It is quite common in Haskell to name a variable with a single quote at the end (imitating a prime symbol). Double primes (two single quotes at the end) are also common. Sunlight doesn't seem to handle them very well. The following snippet of Haskell code

``` haskell
c'' = 'a'
```

is displayed as

``` haskell
''' = 'a'
```

with `'''` highlighted as a character literal.
