0024023: Revamp the OCCT Handle - gcc and clang

Adaptations for compiling with GCC 4.7 and 4.8:
- Construction semantics is used for Handle objects being initialized by const Handle objects of derived type, to avoid overload resolution error in GCC 4.7.
- Missing includes added.
- Fixed bugs related to misuse of direct casts of handle.
- Eliminate CLang warnings on uninitialized and unused variables, functions, and expressions

src/StepToTopoDS/StepToTopoDS_GeometricTool.cxx

@@ -103,7 +103,7 @@ Standard_Boolean  StepToTopoDS_GeometricTool::IsSeamCurve
  const Handle(StepShape_Edge)&         StepEdge,
  const Handle(StepShape_EdgeLoop)&     EdgeLoop)
 {
-  if (!Handle(StepGeom_SeamCurve)::DownCast(SurfCurve).IsNull())
+  if (SurfCurve->IsKind(STANDARD_TYPE(StepGeom_SeamCurve)))
     return Standard_True;
   
   if (SurfCurve->NbAssociatedGeometry() != 2) return Standard_False;