Fix HTG Squeeze function and rename HT internal function Frozen to Freeze

Common/DataModel/vtkHyperTree.cxx

@@ -131,7 +131,7 @@ public:
   static vtkCompactHyperTree* New();
 
   //---------------------------------------------------------------------------
-  vtkHyperTree* Frozen( ) override
+  vtkHyperTree* Freeze( ) override
   {
     return this;
   }

Common/DataModel/vtkHyperTree.h

@@ -183,7 +183,7 @@ public:
   /**
    * JB Return a frozen instance (a priori compact but potentially not changeable).
    */
-  virtual vtkHyperTree* Frozen() = 0;
+  virtual vtkHyperTree* Freeze() = 0;
 
   //@{
   /**

Common/DataModel/vtkHyperTreeGrid.cxx

@@ -178,10 +178,9 @@ void vtkHyperTreeGrid::Squeeze()
     vtkHyperTreeGridIterator itIn;
     InitializeTreeIterator( itIn );
     vtkIdType indexIn;
-    vtkHyperTree *ht = vtkHyperTree::SafeDownCast( itIn.GetNextTree( indexIn  ) );
-    while ( ht )
+    while ( vtkHyperTree *ht = itIn.GetNextTree( indexIn  ) )
     {
-      vtkHyperTree *htfrozen = ht->Frozen();
+      vtkHyperTree *htfrozen = ht->Freeze();
       if ( htfrozen != ht )
       {
         this->SetTree( indexIn, htfrozen );