This brings a more modern Mono release to the ports tree. After
discussions with others in the Mono community I targeted the mono
184.108.40.206 release which is the latest release in the "Visual Studio"
release channel. This is considered to be the most stable and widely
tested, which makes it a good candidate for us. We may upgrade to 5.12
after additional testing or introduce another Mono package for users who
require testing against a newer release; this has yet to be determined.
- Build from official release tarballs
- Now include BoringSSL per upstream guidelines 
- Remove ACCEPTANCE_TESTS, not being updated by upstream
- No long require glib; Mono includes their own replacement
- USES=display:tests required for some tests
- Remove broken for armv6, armv7: file now available 
- Mark as LLD safe as mono changed how it handles TLS