VS 2015 - Clang/C2 Pre-Release

This release adds support for Clang/C2 with VS 2015 Update 1 as described on http://blogs.msdn.com/b/vcblog/archive/2015/12/04/introducing-clang-with-microsoft-codegen-in-vs-2015-update-1.aspx

Clang/C2 can be specified as the Toolset
cmake -G "Visual Studio 14 2015" -T v140_clang_3_7 ...

Or for a specific project, the toolset can be overridden using the VS_PLATFORM_TOOLSET_OVERRIDE variable as in:
set_property(TARGET TestClang PROPERTY VS_PLATFORM_TOOLSET_OVERRIDE "v140_clang_3_7")

We'd love to hear your feedback on this, what works and what doesn't, how we can make things better.