circleSet: Corrected point ordering

Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1932

src/sampling/sampledSet/circle/circleSet.C

@@ -118,7 +118,10 @@ void Foam::circleSet::calcSamples
             samplingCells.append(cellI);
             samplingFaces.append(-1);
             samplingSegments.append(nPoint);
-            samplingCurveDist.append(mag(pt - startPoint_));
+            samplingCurveDist.append
+            (
+                radius*constant::mathematical::pi/180.0*theta
+            );
 
             nPoint++;
         }