message: [c#] Address issue with Mono .mdb -> .pdb change
  Handle Mono build producing either a .mdb or a .pdb file.
diff: <DocumentationFile>$(OutDir)\$(TargetName).xml</DocumentationFile>
  </PropertyGroup>
  <ItemGroup>
  - <FileToCopy Include="$(TargetDir)\$(TargetName).pdb" Condition="'$(OS)' != 'Unix'" />
  - <FileToCopy Include="$(TargetPath).mdb" Condition="'$(OS)' == 'Unix'" />
  + <FileToCopy Include="$(TargetDir)\$(TargetName).pdb" Condition="'$(MSBuildRuntimeType)' != 'Mono' or '$(_DebugFileExt)' == '.pdb'" />
  + <FileToCopy Include="$(TargetPath).mdb" Condition="'$(MSBuildRuntimeType)' == 'Mono' and '$(_DebugFileExt)' == '.mdb'" />
  <FileToCopy Include="$(OutDir)\$(TargetName).xml" />
  </ItemGroup>
  <Target Name="AfterBuild">
  