lang/zephir: Update 0.17.0 => 0.19.0

Changelogs:
https://github.com/zephir-lang/zephir/releases/tag/0.18.0
https://github.com/zephir-lang/zephir/releases/tag/0.19.0

• Replace PORTVERSION with DISTVERSION.
• Replace custom do-extract (CP) with "EXTRACT_CMD=${CP}".
• Split long lines in do-install.
• Repalce "${LN} -s" with "${RLN}".

PR: 293619
Approved by: R. Christian McDonald <rcm@rcm.sh> (maintainer, timeout 2 weeks)
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>