Update www/falkon to the latest release.
Release notes https://www.falkon.org/2018/05/08/falkon-301-released/
There's one bit of trickery here, which handles QtWebEngine < 5.10 mixed
with newer Qt -- just the situation the ports tree is in today.
Thanks to Ken Moore for providing partial patches for OPTION KWALLET.
PR: 235681 235680 234692
Reported by: Nuno Teixeira, Ken Moore