[Haddock] display of unpacked constructors

[Ganesh Sittampalam]

Hi,

It seems as if "!!" is used to denote constructors that are marked with an 
UNPACK pragma:

http://hackage.haskell.org/packages/archive/bytestring/0.9.1.4/doc/html/Data-ByteString-Internal.html#v:PS

While this looks nice, it seems like a potential source of confusion for 
people reading the documentation. Someone on #haskell was asking about 
what it meant today and it took a while to track down what was going on.

I'd suggest that haddock should stay faithful to the source syntax even if 
the results are uglier.

Cheers,

Ganesh