Support the creation of >= 3.x OpenGL contexts

Use the EGL_KHR_create_context extension if available to create modern gl
contexts. We disable window decorations on core profiles because that
mandates a VAO to be used.

Change-Id: Id6044e64f6736244ae9d593af4d68c4000a31de6
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/wayland/qwaylandwindow.cpp

@@ -700,7 +700,6 @@ bool QWaylandWindow::setWindowStateInternal(Qt::WindowState state)
     // QPlatformWindow::setWindowState returns, so we cannot rely on QWindow::windowState
     // here. We use then this mState variable.
     mState = state;
-    createDecoration();
 
     if (mShellSurface) {
         switch (state) {