client/nested: reuse weston-egl-ext.h declarations

Rather than introducing a local copy of the
EGL_WL_create_wayland_buffer_from_image (re)definition, just use the
local header.

This also gives us access to EGL_WL_bind_wayland_display which is also
used in the client, yet the C file is missing a fall-back definition.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

clients/nested.c

@@ -50,15 +50,8 @@
 #include "shared/xalloc.h"
 #include "window.h"
 
-#ifndef EGL_WL_create_wayland_buffer_from_image
-#define EGL_WL_create_wayland_buffer_from_image 1
+#include "weston-egl-ext.h"
 
-#ifdef EGL_EGLEXT_PROTOTYPES
-EGLAPI struct wl_buffer * EGLAPIENTRY eglCreateWaylandBufferFromImageWL(EGLDisplay dpy, EGLImageKHR image);
-#endif
-typedef struct wl_buffer * (EGLAPIENTRYP PFNEGLCREATEWAYLANDBUFFERFROMIMAGEWL) (EGLDisplay dpy, EGLImageKHR image);
-
-#endif
 
 static int option_blit;