Changed selectCount() to not alter the state of the Query,

so that I can select a count of matching rows and then go on
to add an ordering and limit and select a particular page of results.

src/main/java/com/samskivert/depot/Query.java

@@ -358,8 +358,7 @@ public class Query<T extends PersistentRecord>
     public int selectCount ()
     {
         checkState(_groupBy == null, "Do you mean to select(Funcs.countStar())?");
-        _fromOverride = new FromOverride(_pclass);
-        return _repo.load(CountRecord.class, _cache, getClauseArray()).count;
+        return _repo.load(CountRecord.class, _cache, override(_pclass).getClauseArray()).count;
     }
 
     /**