Wayland: Fix window hiding

Corrects the protocol violation when creating an xdg_surface from a
wl_surface that already has a buffer due to EGL buffer swaps.

This commit is based on PR #1731 by @ghost, but adapted and altered:
 - The XDG surface and role are now only created when a window is shown
   to prevent application lists from showing command-line applications
   with off-screen-only windows
 - The special case of Wayland+EGL buffer swap is now in the EGL code
   to mirror how X11 is handled
 - Adaption to run-time platform selection and separate credits file

Fixes #1492
Closes #1731

src/egl_context.c

@@ -231,6 +231,15 @@ static void swapBuffersEGL(_GLFWwindow* window)
         return;
     }
 
+#if defined(_GLFW_WAYLAND)
+    if (_glfw.platform.platformID == GLFW_PLATFORM_WAYLAND)
+    {
+        // NOTE: Swapping buffers on a hidden window on Wayland makes it visible
+        if (!window->wl.visible)
+            return;
+    }
+#endif
+
     eglSwapBuffers(_glfw.egl.display, window->context.egl.surface);
 }