Make compression negotiation more lenient

[abursavich]

I ran into a server this morning that was being extra-super-duper explicit and specifying server_max_window_bits=15, so I started digging into the RFC and the negotiation code... These are the changes I would like to make:

1. Client allows server to specify server_max_window_bits: The server may use a smaller sliding window for compression without affecting the client's decompression.
2. Server allows client to specify server_max_window_bits=15: Although the server can't support a smaller sliding window at the moment, it doesn't hurt to accept the specification of 15 bits from a client.
3. Server declines unacceptable compression offers without rejecting the request and selects the first acceptable offer: According to the RFC, the client may send multiple offers in its preferential order and the server may accept its preferred offer or decline all of them. Declining a compression offer doesn't mean the connection must be terminated.
4. Removes dead x-webkit-deflate-frame code.

[abursavich]

The RFCs allow for some strange formatting of the extensions. For instance, the parameter values may be quoted (e.g. server_max_window_bits="15"). I went ahead and implemented full parsing in a different branch. It's not necessary to fix the specific issue I ran into, but it's here if you're interested: abursavich/websocket@compression...abursavich:headers

[nhooyr]

Thanks for contributing @abursavich! <3

Unfortunately I'm going to be a busy this week until the weekend. I'll try and review these changes then.

Have a great rest of your week!

[nhooyr]

Beautiful, sorry for the delay.

[nhooyr]

Thanks @abursavich!