Update Microsoft.Net.ToolsetCompilers and Microsoft.Net.RoslynDiagnostics to version 1.0.0-rc1-20150116-01.

Also turn on the DeclarePublicAPI analyzer for all of the C# assemblies that end up in our NuGet packages. I can't turn the DeclarePublicAPI analyzer on for our VB projects yet due to bugs in the analyzer driver. (changeset 1400249)