checkMesh: Added option to write sets

- the checking for point-connected multiple-regions now also writes the
    conflicting points to a pointSet
  - with the -writeSets option it now also reconstructs & writes pointSets

applications/utilities/mesh/manipulation/checkMesh/checkTopology.H

@@ -1,5 +1,6 @@
 #include "label.H"
 #include "autoPtr.H"
+#include "writer.H"
 
 namespace Foam
 {
@@ -11,6 +12,7 @@ namespace Foam
         const polyMesh&,
         const bool,
         const bool,
-        const autoPtr<surfaceWriter>&
+        const autoPtr<surfaceWriter>&,
+        const autoPtr<writer<scalar>>&
     );
 }