Update Makefile in terms of C# sources and keyfile command line option
Update Makefile in terms of C# sources and keyfile command line option

committer: Jon Skeet <202926418fe28ce7b8564dbdb1a543a31acbf038@pobox.com>

plutoo/protobuf-csharp-port,happydpc/protobuf-csharp-port,plutoo/protobuf-csharp-port,happydpc/protobuf-csharp-port,evgenekov/protobuf-csharp-port,happydpc/protobuf-csharp-port,evgenekov/protobuf-csharp-port,plutoo/protobuf-csharp-port,evgenekov/protobuf-csharp-port,evgenekov/protobuf-csharp-port,plutoo/protobuf-csharp-port,happydpc/protobuf-csharp-port