Remove old docs, rename docs_new to docs

It would be probably good idea to also remove tools/docgen.py and
asciidoc.mk, but asciidoc.mk is still mentioned under `cloud/doc`, which
may contain some useful info which we'll need at least to review before
removing.

PUBLISHED_FROM=faf454d4c52a2f07ea8ac084cf0bd11a0c9c9b3b

docs/c-api/dns-server.h/mg_dns_create_reply.md

@@ -0,0 +1,36 @@
+---
+title: "mg_dns_create_reply()"
+decl_name: "mg_dns_create_reply"
+symbol_kind: "func"
+signature: |
+  struct mg_dns_reply mg_dns_create_reply(struct mbuf *io,
+                                          struct mg_dns_message *msg);
+---
+
+Create a DNS reply.
+
+The reply will be based on an existing query message `msg`.
+The query body will be appended to the output buffer.
+"reply + recursion allowed" will be added to the message flags and
+message's num_answers will be set to 0.
+
+Answer records can be appended with `mg_dns_send_reply` or by lower
+level function defined in the DNS API.
+
+In order to send the reply use `mg_dns_send_reply`.
+It's possible to use a connection's send buffer as reply buffers,
+and it will work for both UDP and TCP connections.
+
+Example:
+
+```c
+reply = mg_dns_create_reply(&nc->send_mbuf, msg);
+for (i = 0; i < msg->num_questions; i++) {
+  rr = &msg->questions[i];
+  if (rr->rtype == MG_DNS_A_RECORD) {
+    mg_dns_reply_record(&reply, rr, 3600, &dummy_ip_addr, 4);
+  }
+}
+mg_dns_send_reply(nc, &reply);
+``` 
+