vim-patch:8.1.2225: the "last used" info of a buffer is under used

Problem:    The "last used" info of a buffer is under used.
Solution:   Add "lastused" to getbufinfo(). List buffers sorted by last-used
            field. (Andi Massimino, closes vim/vim#4722)
52410575be

src/nvim/eval.c

@@ -7241,6 +7241,8 @@ dict_T *get_buffer_info(buf_T *buf)
     tv_dict_add_list(dict, S_LEN("signs"), get_buffer_signs(buf));
   }
 
+  tv_dict_add_nr(dict, S_LEN("lastused"), buf->b_last_used);
+
   return dict;
 }