[CMake] include_directories and relative paths

[John Drescher]

> I don't need to move/copy "CMake build tree", I just want to generate
> and move/copy "VC proj/solution files".

You can not generate portable Visual Studio solution files with CMake.
The solution files generated would still require CMake. Its best not
to even package these. Just use CMake on all development machines and
generate your builds separately.
John