0024228: TKOpenGL - destroy GL context at view close

- OpenGl_Display - release GL resources correctly on closing views
- OpenGl_AspectFace, OpenGl_AspectText, OpenGl_AspectLine, OpenGl_AspectMarker - initialize OpenGl resources on demand, when context is available.
- Graphic3d_TextureRoot - use const modifier for GetId method to avoid asynchronous resource state at OpenGl.
- Do not call OpenGL functions if no active GL context has been left
- Reset thread's context before deletion for Mesa WNT

src/Graphic3d/Graphic3d_TextureRoot.cdl

@@ -82,6 +82,7 @@ is
   -- for each instance of Graphic3d_AspectFillArea3d where texture will be used.
   -- .
   -- @return texture identifier.
+  ---C++: return const &
 
   GetImage (me) returns PixMap_Handle from Image
   is virtual;

src/Graphic3d/Graphic3d_TextureRoot.cxx

@@ -108,7 +108,7 @@ void Graphic3d_TextureRoot::Destroy() const
 // function : GetId
 // purpose  :
 // =======================================================================
-TCollection_AsciiString Graphic3d_TextureRoot::GetId() const
+const TCollection_AsciiString& Graphic3d_TextureRoot::GetId() const
 {
   return myTexId;
 }