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_parse_http.md

@@ -0,0 +1,15 @@
+---
+title: "mg_parse_http()"
+decl_name: "mg_parse_http"
+symbol_kind: "func"
+signature: |
+  int mg_parse_http(const char *s, int n, struct http_message *hm, int is_req);
+---
+
+Parse a HTTP message.
+
+`is_req` should be set to 1 if parsing request, 0 if reply.
+
+Return number of bytes parsed. If HTTP message is
+incomplete, `0` is returned. On parse error, negative number is returned. 
+