more sensible SdrObject::Clone() and SdrObject::operator=()

Virtual operator=() is IMO pointless, and especially in a class hierarchy
like SdrObject it's pretty unlikely one could reasonably assign any
SdrObject-based object to any other one. Moreover, it was actually
only used in Clone(), which was almost never reimplemented, so the
more sensible choice is to have non-virtual operator= and virtual
Clone() always being reimplemented and using that.

This commit also fixes various smaller or bigger, er, interesting
details in the various operator= implementations.

basctl/source/dlged/dlgedobj.cxx

@@ -979,16 +979,14 @@ void DlgEdObj::clonedFrom(const DlgEdObj* _pSource)
 
 //----------------------------------------------------------------------------
 
-SdrObject* DlgEdObj::Clone() const
+DlgEdObj* DlgEdObj::Clone() const
 {
-    SdrObject* pReturn = SdrUnoObj::Clone();
-
-    DlgEdObj* pDlgEdObj = PTR_CAST(DlgEdObj, pReturn);
+    DlgEdObj* pDlgEdObj = CloneHelper< DlgEdObj >();
     DBG_ASSERT( pDlgEdObj != NULL, "DlgEdObj::Clone: invalid clone!" );
     if ( pDlgEdObj )
         pDlgEdObj->clonedFrom( this );
 
-    return pReturn;
+    return pDlgEdObj;
 }
 
 //----------------------------------------------------------------------------
@@ -1005,13 +1003,6 @@ SdrObject* DlgEdObj::getFullDragClone() const
 
 //----------------------------------------------------------------------------
 
-void DlgEdObj::operator= (const SdrObject& rObj)
-{
-    SdrUnoObj::operator= (rObj);
-}
-
-//----------------------------------------------------------------------------
-
 void DlgEdObj::NbcMove( const Size& rSize )
 {
     SdrUnoObj::NbcMove( rSize );

basctl/source/inc/dlgedobj.hxx

@@ -104,8 +104,7 @@ public:
     virtual sal_uInt32 GetObjInventor() const;
     virtual sal_uInt16 GetObjIdentifier() const;
 
-    virtual SdrObject*  Clone() const;                                          // not working yet
-    virtual void        operator= (const SdrObject& rObj);                      // not working yet
+    virtual DlgEdObj*   Clone() const;                                          // not working yet
     virtual void clonedFrom(const DlgEdObj* _pSource);                          // not working yet
 
     // FullDrag support