Multi-part Websockets broken - here's a fix

[MightyPork]

It sends OpCode other than 0 ("CONT") in the continuation frames, which does not work (browser throws an error). This happens if you use WEBSOCK_FLAG_CONT to send multiple chained messages.

I fixed this in my fork by adding WEBSOCK_FLAG_MORE

Now: WEBSOCK_FLAG_MORE = no FIN, WEBSOCK_FLAG_CONT = opcode 0. Works perfectly!

MightyPork@1a69994

Not sure if you want a PR or not, I already have a bunch of other improvements there. But this is the first bug I found.