Now LWIP_PLATFORM_ASSERT has been fixed we're seeing an assert for the
ping example app.
It sets the SO_RCVTIMEO socket option which is not enabled.
Fixes#308
* Add an example for how to enable TLS verification.
TLS should really be used with verification enabled, as otherwise you
can still suffer from a "man in the middle" attack. Add an example that
demonstrates how to do this.
Fixes#337
