fix the problem with the security margin (Herdt algorithm)

src/Mathematics/relative-feet-inequalities.cpp

src/ZMPRefTrajectoryGeneration/ZMPVelocityReferencedQP.cpp

src/ZMPRefTrajectoryGeneration/generator-vel-ref.cpp

src/ZMPRefTrajectoryGeneration/qp-problem.cpp

tests/CommonTools.cpp

tests/TestHerdt2010DynamicFilter.cpp

tests/TestMorisawa2007.cpp