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/http.h/mg_serve_http.md

@@ -0,0 +1,28 @@
+---
+title: "mg_serve_http()"
+decl_name: "mg_serve_http"
+symbol_kind: "func"
+signature: |
+  void mg_serve_http(struct mg_connection *nc, struct http_message *hm,
+                     struct mg_serve_http_opts opts);
+---
+
+Serve given HTTP request according to the `options`.
+
+Example code snippet:
+
+```c
+static void ev_handler(struct mg_connection *nc, int ev, void *ev_data) {
+  struct http_message *hm = (struct http_message *) ev_data;
+  struct mg_serve_http_opts opts = { .document_root = "/var/www" };  // C99
+
+  switch (ev) {
+    case MG_EV_HTTP_REQUEST:
+      mg_serve_http(nc, hm, opts);
+      break;
+    default:
+      break;
+  }
+}
+``` 
+