Position calculations in HsParser

[Simon Marlow]

> HsParser miscalculates column-positions if qualified names are used.
> The problem seems to be the lexer forgetting to count the '.' in the
> qualified name when deciding how much to move forward. In this
> function, for instance,
> 
>     f M.A M.B M.C = 0
>                ^
> 
> HsParser reports that the '=' is located at the column marked 
> by the ^.

Fixed; thanks.

Simon