libmpv: deprecate MPV_RENDER_PARAM_AMBIENT_LIGHT render parameter

the equivalent options have been deprecated since mpv 0.35 in ac39661
and 2207236.

also bumping the MPV_CLIENT_API_VERSION to 2.5, since 2.4 was forgotten
in 6f619d5.

DOCS/client-api-changes.rst

@@ -32,6 +32,8 @@ API changes
 
 ::
 
+ --- mpv 0.40.0 ---
+ 2.5    - Deprecate MPV_RENDER_PARAM_AMBIENT_LIGHT. no replacement.
  --- mpv 0.39.0 ---
  2.4    - mpv_render_param with the MPV_RENDER_PARAM_ICC_PROFILE argument no
           longer has incorrect assumptions about memory allocation and can be

libmpv/render.h

@@ -225,6 +225,7 @@ typedef enum mpv_render_param_type {
      */
     MPV_RENDER_PARAM_ICC_PROFILE = 6,
     /**
+     * Deprecated
      * Ambient light in lux. Valid for mpv_render_context_set_parameter().
      * Type: int*
      * This can be used for automatic gamma correction.

video/out/gpu/libmpv_gpu.c

@@ -111,6 +111,7 @@ static int set_parameter(struct render_backend *ctx, mpv_render_param param)
         return 0;
     }
     case MPV_RENDER_PARAM_AMBIENT_LIGHT: {
+        MP_WARN(ctx, "MPV_RENDER_PARAM_AMBIENT_LIGHT is deprecated and might be removed in the future (no replacement)\n");
         int lux = *(int *)param.data;
         gl_video_set_ambient_lux(p->renderer, lux);
         return 0;