ENH: make search of instances in IOobject::typeHeaderOk optional (issue #245)

- in specific cases it can be useful to suppress searching the instances.
  For example, if one only wishes to check if a "points" is available at
  the given time instance, without searching backwards through all
  times.

applications/utilities/postProcessing/dataConversion/foamToEnsight/checkMeshMoving.H

@@ -7,8 +7,6 @@ if (timeDirs.size() > 1 && Pstream::master())
     // We already loaded a mesh (usually from constant).
     // See if any other "polyMesh/points" files exist too.
 
-    const fileName& baseDir = mesh.time().path();
-
     Info<< "Search for moving mesh ... " << flush;
     forAll(timeDirs, timeI)
     {
@@ -17,7 +15,6 @@ if (timeDirs.size() > 1 && Pstream::master())
         meshMoving =
         (
             timeName != mesh.pointsInstance()
-         && isDir(baseDir/timeName/polyMesh::meshSubDir)
          && IOobject
             (
                 "points",
@@ -27,7 +24,7 @@ if (timeDirs.size() > 1 && Pstream::master())
                 IOobject::NO_READ,
                 IOobject::NO_WRITE,
                 false  // no register
-            ).typeHeaderOk<pointIOField>(true)
+            ).typeHeaderOk<pointIOField>(true, false)
         );
 
         if (meshMoving)