Added option to disable compilation of contrib code
Added option to disable compilation of contrib code

bassosimone/yaml-cpp,steinwurf/yaml-cpp,eacousineau/yaml_cpp_0_2_7,eacousineau/yaml_cpp_0_2_7,bassosimone/yaml-cpp,steinwurf/yaml-cpp,steinwurf/yaml-cpp,bassosimone/yaml-cpp,bassosimone/yaml-cpp,steinwurf/yaml-cpp