cogl/egl: Restore support for EGL 1.4

It was dropped in 46.0 (683e917854) but we've now found that Xilinx Mali
only implements a strict interpretation of 1.4 [1] which doesn't support
looking up core functions [2] such as `glGetString`.

[1] https://github.com/Xilinx/mali-userspace-binaries/blob/master/Standards.txt
[2] https://registry.khronos.org/EGL/specs/eglspec.1.4.pdf § 3.10

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4019>

cogl/cogl/winsys/cogl-winsys-egl.c

@@ -110,7 +110,12 @@ static GCallback
 _cogl_winsys_renderer_get_proc_address (CoglRenderer *renderer,
                                         const char   *name)
 {
-  return eglGetProcAddress (name);
+  GCallback result = eglGetProcAddress (name);
+
+  if (result == NULL)
+    g_module_symbol (renderer->libgl_module, name, (gpointer *)&result);
+
+  return result;
 }
 
 static void