devices: --devices/--specials/-D/--copy-devices/--write-devices

Recreate char/block nodes via mknodat (privilege-gated, EPERM->warn+skip) and
FIFOs via mkfifoat; new STATUS_SPECIAL frame + validated rdev; sockets skipped;
-copy-devices copies st_size; -write-devices O_NOFOLLOW+O_NONBLOCK warn+skip.
preserve_specials/copy_devices/write_devices cross the wire. PROTOCOL_VERSION
2.12.0->2.13.0. Review fixes: -m source-removal keeps recreated specials, FIFO
ENXIO skip, rdev bounds at chunk_deserialize, STATUS_ERROR on receive branch,
scanner_prepare_special dedup.

src/client/client_send.c

@@ -104,6 +104,9 @@ static bool prepare_scanner(const Config* config, int num_threads, PreparedScann
   options->copy_unsafe_links = config->copy_unsafe_links;
   options->checksum = config->checksum;
   options->one_file_system = config->one_file_system;
+  options->preserve_devices = config->preserve_devices;
+  options->preserve_specials = config->preserve_specials;
+  options->copy_devices = config->copy_devices;
   options->file_list = (const FileListSet*)config->files_from_set;
   options->base_filters = out->base_filters;
   options->per_dir_filters = config->per_dir_filter;
@@ -1248,6 +1251,14 @@ static int send_chunk_with_removal(Client* client, Chunk* chunk, Config* config,
       change_emit_file_sent(config, f);
       continue;
     }
+    /* --devices/--specials: a device/special node is recreated on the receiver,
+       not transferred as content.  Send the dedicated STATUS_SPECIAL frame. */
+    if (f->is_special) {
+      if (!file_send_special(f, client->file_descriptor, config->use_metadata))
+        return -1;
+      change_emit_file_sent(config, f);
+      continue;
+    }
     bool stream = f->data->data == NULL && f->data->size > 0;
     bool use_sendfile =
         (config->use_sendfile && !config->use_compression) || (stream && !config->use_compression);