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/json-rpc.h/mg_rpc_parse_reply.md

@@ -0,0 +1,24 @@
+---
+title: "mg_rpc_parse_reply()"
+decl_name: "mg_rpc_parse_reply"
+symbol_kind: "func"
+signature: |
+  int mg_rpc_parse_reply(const char *buf, int len, struct json_token *toks,
+                         int max_toks, struct mg_rpc_reply *,
+                         struct mg_rpc_error *);
+---
+
+Parse JSON-RPC reply contained in `buf`, `len` into JSON tokens array
+`toks`, `max_toks`. If buffer contains valid reply, `reply` structure is
+populated. The result of RPC call is located in `reply.result`. On error,
+`error` structure is populated. Returns: the result of calling
+`parse_json(buf, len, toks, max_toks)`:
+
+On success, an offset inside `json_string` is returned
+where parsing has finished. On failure, a negative number is
+returned, one of:
+
+- `#define JSON_STRING_INVALID           -1`
+- `#define JSON_STRING_INCOMPLETE        -2`
+- `#define JSON_TOKEN_ARRAY_TOO_SMALL    -3` 
+