libs: libwebsockets: add latest released version

This includes a patch for cyassl building that has been committed
upstream, but not released.

No SPDX license identifier is used, as this is LGPL+linking exception,
which doesn't seem to be covered by SPDX.

See also: https://github.com/warmcat/libwebsockets/issues/170

Signed-off-by: Karl Palsson <karlp@remake.is>
Correct spelling is PKG_LICENSE_FILES