storage: enable the test of a share larger than 2 GiB; this will probably be too expensive on Mac OS X, but I think it won't be on all the other platforms ; I will probably set it to SkipTest if the sys.platform is Mac after seeing the results of this buildbot run

src/allmydata/test/test_storage.py

@@ -267,7 +267,6 @@ class Server(unittest.TestCase):
         readers = ss.remote_get_buckets("allocate")
         reader = readers[shnum]
         self.failUnlessEqual(reader.remote_read(2**32, 2), "ab")
-    test_large_share.skip = "This test is too expensive on systems without efficient sparse files."
 
     def test_dont_overfill_dirs(self):
         """