wined3d: Make the device parameter to wined3d_device_get_index_buffer() const.

dlls/wined3d/device.c

@@ -2402,7 +2402,7 @@ HRESULT CDECL wined3d_device_set_index_buffer(struct wined3d_device *device,
     return WINED3D_OK;
 }
 
-HRESULT CDECL wined3d_device_get_index_buffer(struct wined3d_device *device, struct wined3d_buffer **buffer)
+HRESULT CDECL wined3d_device_get_index_buffer(const struct wined3d_device *device, struct wined3d_buffer **buffer)
 {
     TRACE("device %p, buffer %p.\n", device, buffer);
 

include/wine/wined3d.h

@@ -2221,7 +2221,8 @@ HRESULT __cdecl wined3d_device_get_display_mode(struct wined3d_device *device,
 HRESULT __cdecl wined3d_device_get_front_buffer_data(struct wined3d_device *device,
         UINT swapchain_idx, struct wined3d_surface *dst_surface);
 void __cdecl wined3d_device_get_gamma_ramp(struct wined3d_device *device, UINT swapchain_idx, WINED3DGAMMARAMP *ramp);
-HRESULT __cdecl wined3d_device_get_index_buffer(struct wined3d_device *device, struct wined3d_buffer **index_buffer);
+HRESULT __cdecl wined3d_device_get_index_buffer(const struct wined3d_device *device,
+        struct wined3d_buffer **index_buffer);
 HRESULT __cdecl wined3d_device_get_light(const struct wined3d_device *device, UINT light_idx, WINED3DLIGHT *light);
 HRESULT __cdecl wined3d_device_get_light_enable(const struct wined3d_device *device, UINT light_idx, BOOL *enable);
 HRESULT __cdecl wined3d_device_get_material(const struct wined3d_device *device, WINED3DMATERIAL *material);