imgutils: Use designated initializers for AVClass

More readable and less breakable.

libavutil/imgutils.c

@@ -236,11 +236,21 @@ typedef struct ImgUtils {
     void *log_ctx;
 } ImgUtils;
 
-static const AVClass imgutils_class = { "IMGUTILS", av_default_item_name, NULL, LIBAVUTIL_VERSION_INT, offsetof(ImgUtils, log_offset), offsetof(ImgUtils, log_ctx) };
+static const AVClass imgutils_class = {
+    .class_name = "IMGUTILS",
+    .item_name  = av_default_item_name,
+    .version    = LIBAVUTIL_VERSION_INT,
+    .log_level_offset_offset   = offsetof(ImgUtils, log_offset),
+    .parent_log_context_offset = offsetof(ImgUtils, log_ctx),
+};
 
 int av_image_check_size(unsigned int w, unsigned int h, int log_offset, void *log_ctx)
 {
-    ImgUtils imgutils = { &imgutils_class, log_offset, log_ctx };
+    ImgUtils imgutils = {
+        .class      = &imgutils_class,
+        .log_offset = log_offset,
+        .log_ctx    = log_ctx,
+    };
 
     if ((int)w>0 && (int)h>0 && (w+128)*(uint64_t)(h+128) < INT_MAX/8)
         return 0;