0025422: Visualization, TKOpenGl - support re-assignment of new window to existing View

Do not throw "Window already defined" exception in Visual3d_View/V3d_View.
Handle window change within OpenGl_GraphicDriver::View().

OpenGl_GraphicDriver - introduce dedicated methods to initialize/release shared OpenGL context.
::InitEglContext() to using existing EGL context.

OpenGl_Context - always enable NPOT textures on OpenGL ES 2.0

OpenGl_Workspace - do not call glDisable/glEnable(GL_TEXTURE_2D) on GL ES

OpenGl_GraphicDriver::ReleaseContext() - release EGL context on destruction

OpenGl_GraphicDriver::InitEglContext() - escape method implementation with HAVE_EGL macros

OpenGl_ShaderManager - clear shader programs on shared context invalidation

src/OpenGl/OpenGl_Workspace.cxx

@@ -337,8 +337,8 @@ Handle(OpenGl_Texture) OpenGl_Workspace::DisableTexture()
           glDisable (GL_POINT_SPRITE);
         }
       }
-    #endif
       glDisable (GL_TEXTURE_2D);
+    #endif
       break;
     }
     default: break;
@@ -562,8 +562,8 @@ void OpenGl_Workspace::setTextureParams (Handle(OpenGl_Texture)&
         glEnable (GL_TEXTURE_GEN_S);
         glEnable (GL_TEXTURE_GEN_T);
       }
-    #endif
       glEnable (GL_TEXTURE_2D);
+    #endif
       break;
     }
     default: break;