tcfail175: error message changed

* The error message has become less informative, but I don't see how to avoid
  this easily.
* The error message is now also different to that of 6.8.  I am not sure how
  to handle this case.  Can we have different stderr files for different
  compiler versions?  Or shall we simply merge the corresponding changes
  into 6.8?

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail175.stderr

 
 tcfail175.hs:11:0:
-    The equation(s) for `evalRHS' have three arguments,
-    but its type `Int -> a' has only one
+    Couldn't match expected type `a'
+	   against inferred type `String -> String -> String'