[CMake] detecting if c++11 available

[Brad Bell]

My goal is to use some new c++11 features if they are available, 
otherwise to stick to the c++03 features. I need to build test programs 
that check for correctness as well as distribute an include file library.

Is there a way in cmake to detect if c++11 is available and to use it 
when it is available ? I would like this to be system and compiler 
independent.