print/latex-beamer: update 3.57 → 3.71

Changelogs:
https://github.com/josephwright/beamer/blob/v3.71/CHANGELOG.md

Improve port:

• replace PORTVERSION with DISTVERSION;
• add LICENSE_FILE_*;
• pet portclippy.

PR: 282110
Approved by: hrs (maintainer, timeout > 3 months)