third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/csharp/Google.Protobuf.Tools.nuspec

 <?xml version="1.0" encoding="utf-8"?>
 <package>
   <metadata>
     <id>Google.Protobuf.Tools</id>
     <title>Google Protocol Buffers tools</title>
     <summary>Tools for Protocol Buffers - Google's data interchange format.</summary>
     <description>See project site for more info.</description>
-    <version>3.0.0-beta3</version>
+    <version>3.1.0</version>
     <authors>Google Inc.</authors>
     <owners>protobuf-packages</owners>
     <licenseUrl>https://github.com/google/protobuf/blob/master/LICENSE</licenseUrl>
     <projectUrl>https://github.com/google/protobuf</projectUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <releaseNotes>Tools for Protocol Buffers</releaseNotes>
     <copyright>Copyright 2015, Google Inc.</copyright>
     <tags>Protocol Buffers Binary Serialization Format Google proto proto3</tags>
   </metadata>
   <files>
     <file src="protoc\windows_x86\protoc.exe" target="tools\windows_x86\protoc.exe" />
     <file src="protoc\windows_x64\protoc.exe" target="tools\windows_x64\protoc.exe" />
     <file src="protoc\linux_x86\protoc" target="tools\linux_x86\protoc" />
     <file src="protoc\linux_x64\protoc" target="tools\linux_x64\protoc" />
     <file src="protoc\macosx_x86\protoc" target="tools\macosx_x86\protoc" />
     <file src="protoc\macosx_x64\protoc" target="tools\macosx_x64\protoc" />
     <file src="..\src\google\protobuf\any.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\api.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\descriptor.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\duration.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\empty.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\field_mask.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\source_context.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\struct.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\timestamp.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\type.proto" target="tools\google\protobuf" />
     <file src="..\src\google\protobuf\wrappers.proto" target="tools\google\protobuf" />
   </files>
 </package>