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_send_http_chunk.md

@@ -0,0 +1,25 @@
+---
+title: "mg_send_http_chunk()"
+decl_name: "mg_send_http_chunk"
+symbol_kind: "func"
+signature: |
+  void mg_send_http_chunk(struct mg_connection *nc, const char *buf, size_t len);
+---
+
+Send buffer `buf` of size `len` to the client using chunked HTTP encoding.
+This function first sends buffer size as hex number + newline, then
+buffer itself, then newline. For example,
+  `mg_send_http_chunk(nc, "foo", 3)` whill append `3\r\nfoo\r\n` string to
+the `nc->send_mbuf` output IO buffer.
+
+NOTE: HTTP header "Transfer-Encoding: chunked" should be sent prior to
+using this function.
+
+NOTE: do not forget to send empty chunk at the end of the response,
+to tell the client that everything was sent. Example:
+
+```
+  mg_printf_http_chunk(nc, "%s", "my response!");
+  mg_send_http_chunk(nc, "", 0); // Tell the client we're finished
+``` 
+