libwebsockets: Add latest release.

Based on version provided in libwebsockets repo, with minor adjustments.

Future plans are to optionize the ssl library to use.
libwebsockets: Only enable ipv6 if the build is ipv6 enabled

Without this, builds on AA will appear to work, with log messages of
"opening websockets listen socket on xxx" but won't actually open them,
as shown by netstat.
libwebsockets: add openssl/cyassl variants

Build two binaries, one for OpenSSL and one for CyaSSL.
CyaSSL version requires a patch, see
https://github.com/warmcat/libwebsockets/pull/161

According to comments on libwebsockets, cyassl needs to be recompiled to
actually _work_  This has only been compile tested.
libwebsockets: drop packaging for example apps

Example apps are useful when you're developing locally, but there's no
reason to build or offer to install 600k+ of test apps for OpenWrt
packages.

(Also, it's very complicated to build them against the right ssl layer
when you allow both to be built)