STYLE: revert bitSet/HashSet setMany() to set() method (issue #837)

- improves backward compatibility and more naming consistency.
  Retain setMany(iter1, iter2) to avoid ambiguity with the
  PackedList::set(index, value) method.

src/finiteArea/faMesh/faMeshDemandDrivenData.C

@@ -1455,7 +1455,7 @@ void Foam::faMesh::calcPointAreaNormalsByQuadricsFit() const
                     procPatch.neighbPoints()[nonGlobalPatchPoints[pointI]];
 
                 labelHashSet faceSet;
-                faceSet.insertMany(pointFaces[curPoint]);
+                faceSet.insert(pointFaces[curPoint]);
 
                 labelList curFaces = faceSet.toc();