libs: libwebsockets: add latest released version
This includes a patch for cyassl building that has been committed
upstream, but not released.
There's no SPDX license identifier for LGPL + static linking exception,
so I've used "LGPL-2.1+exception" as suggested at
http://lwn.net/Articles/378329/
See also: https://github.com/warmcat/libwebsockets/issues/170
Signed-off-by: Karl Palsson <karlp@remake.is>