Haskell: Improve indent and comment support, fix spelling highlighting i...

...ssue and provide source sanity check on save with ghcmod.

Hi again,

Here are a couple of tweaks just to make the initial Haskell support I did early work a little better out the box. Could you please review and give me feedback when you have a moment.

One thing is the PATH tweak, I can understand/predict this may not make everyone happy or is that ok?
Its purely so that if PATH was not adjusted in the shell rc ghcmod could still be found. Any way, I look forward to your point of view.

Kind Regards,
Edward.