THRIFT-3000 patch uses a .NET 4.5 only overload of System.Reflection.PropertyInfo.SetValue, causing test failures on Travis-CI.
This patch enforces:
- use of .NET 4.5 compatible Mono to build C# lib
- use of correct Mono C# compiler and compiler flags for the version of sdk
It makes mandatory to have Mono 3.x or higher to build C#.