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_connect_ws_opt.md

@@ -0,0 +1,17 @@
+---
+title: "mg_connect_ws_opt()"
+decl_name: "mg_connect_ws_opt"
+symbol_kind: "func"
+signature: |
+  struct mg_connection *mg_connect_ws_opt(struct mg_mgr *mgr,
+                                          mg_event_handler_t ev_handler,
+                                          struct mg_connect_opts opts,
+                                          const char *url, const char *protocol,
+                                          const char *extra_headers);
+---
+
+Helper function that creates an outbound WebSocket connection
+
+Mostly identical to mg_connect_ws, but allows to provide extra parameters
+(for example, SSL parameters 
+