isSpace is too slow

[Donald Bruce Stewart]

ndmitchell:
> Hi,
> 
> I'm running a particular benchmark which calls isSpace a lot
> (basically wc -w). There are three ways to do the underlying space
> comparison - using the Haskell Data.Char.isSpace, using the C isspace,
> or using the C iswspace:
> 
> isspace: 0.375
> iswspace: 0.400
> Char.isSpace: 0.672
> 
> Any chance someone could speed this up?  Perhaps just replacing
> isSpace with a direct call to iswspace?

Want to try also the 
    Data.ByteString.Base.isSpaceWord8 :: Word8 -> Bool

We added that originally I think because isSpace was too slow.

-- Don