EPA : HsModule Trailing comments captured incorrectly

For the code below, the the -- non-trailing comment should appear in the priorComments section of the hsmodAnn EPA annotations. It currently shows up in the followingComments.

module EmptyMostly where
   {
   x=4;
-- non-trailing comment
   }

Proposed fix: return comments from the body production in Parser.y, and work them into the priorComments in acsFinal.

Note: this is a sort of detailed note-to self for me (@alanz).

And if we can't get it into 9.2.1 it can be worked around in ExactPrint.