Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/csharp/src/Google.Protobuf/project.json

-{
-  "version": "3.1.0",
-  "title": "Google Protocol Buffers",
-  "description": "See project site for more info.",
-  "authors": [ "Google Inc." ],
-  "copyright": "Copyright 2015, Google Inc.",
-
-  "packOptions": {
-    "summary": "C# runtime library for Protocol Buffers - Google's data interchange format.",
-    "tags": [ "Protocol", "Buffers", "Binary", "Serialization", "Format", "Google", "proto", "proto3" ],
-    "owners": [ "protobuf-packages" ],
-    "licenseUrl": "https://github.com/google/protobuf/blob/master/LICENSE",
-    "projectUrl": "https://github.com/google/protobuf",
-    "releaseNotes": "C# proto3 support",
-    "requireLicenseAcceptance": false,
-    "repository": {
-      "url": "https://github.com/nodatime/nodatime.git"
-    }
-  },
-
-  "buildOptions": {
-    "debugType": "portable",
-    "keyFile": "../../keys/Google.Protobuf.snk",
-    "xmlDoc": true
-  },
-
-  "configurations": {
-    "Debug": {
-      "buildOptions": {
-        "define": [ "DEBUG", "TRACE" ]
-      }
-    },
-    "Release": {
-      "buildOptions": {
-        "define": [ "RELEASE", "TRACE" ],
-        "optimize": true
-      }
-    }
-  },
-
-  "frameworks": {
-    // This target allows the package to be installed in a .NET 4.5+
-    // project without asking for myriad other dependencies.
-    "net45": {
-    },
-    "netstandard1.0": {
-      "dependencies": {
-        "System.Collections": "4.0.11",
-        "System.Diagnostics.Debug": "4.0.11",
-        "System.Globalization": "4.0.11",
-        "System.IO": "4.1.0",
-        "System.Linq": "4.1.0",
-        "System.Linq.Expressions": "4.1.0",
-        "System.ObjectModel": "4.0.12",
-        "System.Reflection": "4.1.0",
-        "System.Reflection.Extensions": "4.0.1",
-        "System.Runtime": "4.1.0",
-        "System.Runtime.Extensions": "4.1.0",
-        "System.Text.Encoding": "4.0.11",
-        "System.Text.RegularExpressions": "4.1.0",
-        "System.Threading": "4.0.11"
-      }
-    }
-  }
-}