math/yices: Update 2.6.5 => 2.7.0, mark as PIE_UNSAFE

[alven]

Summary

Changelogs:

• https://yices.csl.sri.com/release-notes.html
• https://github.com/SRI-CSL/yices2/compare/Yices-2.6.5...yices-2.7.0

• Switch MASTER_SITES to Github as upstream official site doesn't

contain tarball for 2.7.0
+ Add second WWW for source code repository

• Correct LICENSE and LICENSE_FILE
• Have test issue closed https://github.com/SRI-CSL/yices2/issues/523
• Mark as PIE_UNSAFE

Test Plan

For every {amd64, i386} × {14.3, 13.5}:

• Successful poudriere testport

[yuri]

Approved.

Thanks,
Yuri