sparsehash should either be noarch or keep its universal veriant

[devernay (Frédéric Devernay)]

The following update to the sparsehash port: ​https://github.com/macports/macports-ports/commit/79bcaad0315c9229ee841064701ab8b9fbff47ed removes the +universal variant, but doesn't set noarch, thus preventing dependent ports (eg py27-shiboken) to build a +universal variant

The fix is simply to leave the +universal variant, reverting the above commit. I think it's not a big deal to have a +universal port which is really noarch, and actually identical to the non-universal one.