libwebsockets: bump to 3.1.0
Drops an openssl deprecation patch applied upstream.
Changes since 3.0.0, the following list of websocket related features:
* gzip+brotli compression in the webserver
* threadpools
* string tokenizers
* http reverse proxies
* managed disk cache
Full changes at https://libwebsockets.org/git/libwebsockets/tree/changelog?id=
89eedcaa94e1c8a97ea3af10642fd224bcea068f#n4
Tested on ath79, and classic usage of libwebsockets to provide
websockets support to a C application.
Signed-off-by: Karl Palsson <karlp@etactica.com>