[CMake] Executable and library dependencies

[Emmanuel Blot]

> But then the second parameter is completely superflous, it just adds
> noise and confusion. If you use just add_directory(foo) cmake will
> automatically use <builddir>/foo as builddir for foo.

I don't remember when I've added it, but I *had* to add it at some  
point: CMake was not working as expected before.
Maybe it works fine w/o the second argument by now (2.6.4), but I'm  
sure it uses to fail at some point last year.

Cheers,
Manu