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/struct_websocket_message.md

@@ -0,0 +1,14 @@
+---
+title: "struct websocket_message"
+decl_name: "struct websocket_message"
+symbol_kind: "struct"
+signature: |
+  struct websocket_message {
+    unsigned char *data;
+    size_t size;
+    unsigned char flags;
+  };
+---
+
+WebSocket message 
+