MFH: r477954 r477984 r478349

databases/mantis: Revert fake update from r475644

The checksums and sizes from 2.9.0 and 2.15.0 are identical because
GH_TAGNAME was not updated as well, so the update to 2.15.0 never
actually happened.

PR: 229880
Pointy hat: joneum
Security: 0822a4cf-9318-11e8-8d88-00e04c1ea73d

Take maintainership of databases/mantis

databases/mantis: Update to 2.16.0

• Use upstream release tarball instead of doing our own vendoring
• Add missing PHP extensions
• Flavorize
• Update plugins and install them by default
• Add LICENSE
• Improve pkg-descr

Changes: https://mantisbt.org/bugs/changelog_page.php?project=mantisbt&version=2.16.0
PR: 229880
Reviewed by: dvl, mat, ndowens@yahoo.com
Security: 0822a4cf-9318-11e8-8d88-00e04c1ea73d
Differential Revision: https://reviews.freebsd.org/D16890

Approved by: ports-secteam (miwi)