------------------------------------
	Type signature for derived con2tag
	------------------------------------

		MERGE TO STABLE

The derived con2tag didn't have a type signature, so we got

	con2tagFoo :: a -> Int#
	con2tagFoo = \x -> getTag x

The getTag generates a case expression, so we get a polymorphic
case.  The polymorphic case simply does not work in *interpreted*
GHC 5.02.3 and as a result neither does con2tag.  Alas.

This commit fixes the problem, by giving a type signature for
con2TagFoo.  But note that getTag in interpreted GHC 5.02 will continue
to fail if used in a polymorphic context.  This problem does not arise
in the HEAD (eval/apply) so I'm going to leave it as a wont-fix bug.