Docs are generated for Mongoose

Comments in headers are changed a bit: removed adoc-specific stuff,
markdown is used instead

PUBLISHED_FROM=9242cce85cc52a47a197d377e7e23804721a6bb5

docs/c-api/http.h/mg_send_websocket_handshake2.md

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+---
+title: "mg_send_websocket_handshake2()"
+decl_name: "mg_send_websocket_handshake2"
+symbol_kind: "func"
+signature: |
+  void mg_send_websocket_handshake2(struct mg_connection *nc, const char *path,
+                                    const char *host, const char *protocol,
+                                    const char *extra_headers);
+---
+
+Send websocket handshake to the server.
+
+`nc` must be a valid connection, connected to a server. `uri` is an URI
+to fetch, `host` goes into the `Host` header, `protocol` goes into the
+`Sec-WebSocket-Proto` header (NULL to omit), extra_headers` is extra HTTP
+headers to send or `NULL`.
+
+This function is intended to be used by websocket client. 
+