opengl: We need to return the GLWindow.

Fixes an unitialized read in wglDeleteContext, thanks Dr.Memory!

Change-Id: I3706b18526c48277f9b4a6801c95c26a10a86965

vcl/source/opengl/OpenGLContext.cxx

@@ -180,7 +180,7 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM l
     }
 }
 
-int InitTempWindow(HWND *hwnd, int width, int height, const PIXELFORMATDESCRIPTOR& inPfd, GLWindow glWin)
+int InitTempWindow(HWND *hwnd, int width, int height, const PIXELFORMATDESCRIPTOR& inPfd, GLWindow& glWin)
 {
     PIXELFORMATDESCRIPTOR  pfd = inPfd;
     int  pfmt;