special handling of "Main.hs" contradicts Report

[Mark Tullsen]

I have this simple module:

   module X where
   t1 = t1

If it's in a file called "X.hs," all works as expected,
it exports 't1'.  But if it's in a file called "Main.hs,"
then it doesn't export 't1'.  The same is true if we have
"module Main" instead of "module X".

- Mark