[Position] Use a summation type for the various position types.
[Position] Use a summation type for the various position types.

Rather than using magic values for the row and column field I
think it's cleaner to just define some new constructors for
<builtin position> etc.  The only reason I can see for the way
it was is performance/memory.  But if that was the case Position
would have been defined with newtype.

darcs-hash:20090126085013-db939-b4f3af7ec69c72e4b579cdc8d9ddd7a2269c2290.gz

jthornber/language-c-ejt,jthornber/language-c-ejt,jthornber/language-c-ejt