more accurately test if cmake already installed

(cherry picked from commit 9053936061ee579116e859db5deafa50ac3ce2d0)
update scons to from 2.1.0 to 2.3.4
Merge pull request #131 from PatrickBM/lib_checks

minor updates
add rat-5.0.1
added rat-5.0.2
merge
Merge remote branch 'origin/master' into cvmfs