Skip maessen_hashtab in the 6.8 branch

6.8.2 and soon-to-be-6.8.3 fail it the normal,ghci,threaded1 ways.

testsuite/tests/ghc-regress/programs/maessen-hashtab/test.T

 
-test('maessen_hashtab', composes([reqlib('QuickCheck'),
-                                  skip_if_fast,
-                                  extra_run_opts('99999')]),
+test('maessen_hashtab',
+     composes([reqlib('QuickCheck'),
+               skip_if_fast,
+               if_compiler_lt('ghc', '6.9', skip),
+               extra_run_opts('99999')]),
      multimod_compile_and_run, ['HashTest', '-cpp'])
 clean_o_hi()