0026377: Passing Handle objects as arguments to functions as non-const reference to base type is dangerous

Operator of cast to non-const reference is declared deprecated to produce compiler warning if used (usually implicitly).

OCCT code is updated to avoid that cast, occurring when function accepting non-const reference to handle is called with handle to derived type.
For that, local variable of argument type is passed instead, and down-cast is used to get it to desired type after the call.
A few occurrences of use of uninitialized variable are corrected.

src/StdObjMgt/StdObjMgt_ReadData.hxx

@@ -49,7 +49,9 @@ public:
   template <class Type>
   StdObjMgt_ReadData& operator >> (Handle(Type)& theTarget)
   {
-    ReadReference (theTarget);
+    Handle(StdObjMgt_Persistent) aTarget = theTarget;
+    ReadReference (aTarget);
+    theTarget = Handle(Type)::DownCast (aTarget);
     return *this;
   }