Add ruby26 2.6.3 (copied from ruby25)
PR: 234509 235826
Submitted by: pete@nomadlogic.org (initial revision)
Yasuhiro KIMURA <yasu@utahime.org> (initial revision) meta (myself, minor modifications)
Relnotes:: https://www.ruby-lang.org/en/news/2018/12/25/ruby-2-6-0-released/
https://www.ruby-lang.org/en/news/2019/01/30/ruby-2-6-1-released/ https://www.ruby-lang.org/en/news/2019/03/13/ruby-2-6-2-released/ https://www.ruby-lang.org/en/news/2019/04/17/ruby-2-6-3-released/
Differential Revision: https://reviews.freebsd.org/D19961