isSpace is too slow

[Neil Mitchell]

Hi

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

isspace: 0.375
iswspace: 0.400
ByteString: 0.460
Char: 0.672

Not as fast as isspace/iswspace, but quite a bit faster than Char.
Perhaps someone needs to take a peek at the generated ASM for each of
these routines and see where the Haskell one is falling down.

Thanks

Neil