This copies the VcMacros.cmake and dependent files from Vc master. That
resolves the INCLUDE_DIRECTORIES problem. It also adds -fabi flags to the
PACKAGERS_BUILD macros, which resolves the build problem.

When Vc 1.0 is released, we remove the cmake/vc folder and port to the
new Vc.

Thanks to Matthias Kretz, Alex Merry, Stepen Kelly, Elvis Stansvik for their
help figuring out the issues!