**This review has been split into multiple parts**
//This review remains as a meta review to track the multiple parts//
Individual reviews:
[X] https://reviews.freebsd.org/D13751: ancillary ports
[X] https://reviews.freebsd.org/D13752: mono (and USES=mono)
[] https://reviews.freebsd.org/D14135: msbuild
[] https://reviews.freebsd.org/D16069: lang/fsharp: update to 10.0.2
[] https://reviews.freebsd.org/D16070: devel/monodevelop: update to 7.1.0.1297
[X] https://reviews.freebsd.org/D13869: support linux ports for dotnet-core (CentOS)
[] https://reviews.freebsd.org/D13870: linux-dotnet (depends on support linux ports)
[X] https://reviews.freebsd.org/D14006: lang/mono: update to 5.8.0.108
[X] https://reviews.freebsd.org/D15780: lang/mono: Update to 5.10.1.47