[CMake] Implicity CMAKE_CURRENT_BINARY_DIR include_directories

[Denis Scherbakov]

> On Monday 11 May 2009, Denis Scherbakov wrote:
> > CMAKE_LINK_DEPENDS_DEBUG_MODE is also not documented.
> 
> Is this one an official public variable or may it go away
> again ?

If you ask me - I don't know, I am not a CMake developer.
But there is a lot functionality built around this variable in one of CMake
source files. So I think it is for a long time there.