lang/polyml: Update to 5.8.1

• Bug fix release for version 5.8
• Visual Studio projects have been updated to VS2017 and SDK 10

Changelog: https://github.com/polyml/polyml/releases/tag/v5.8.1

PR: 253282
Submitted by: Wen Heping <wen@FreeBSD.org>
Reviewed by: tcberner (mentor)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D28529