Declarations scanning gets stalled

[k0ral]

The issue was noticed under OS-X and linux, at least.
When opening a haskell file, emacs freezes on the Scanning declarations in file.hs phase.
Reverting PR #580 fixes the issue.

Thank you !

[deviant-logic]

If I read the docs right, looking-at-p differs from looking-at in that it doesn't mutate the match data. Presumably, some of the uses of looking-at in the declaration scanning code actually depended on the side-effect?

[gracjan]

I've reverted in e5afe82. Still, there must be some twisted logic going on if that commit broke scanning.