configure: gromacs 4.5 was released, moved warning about devel version to gmx 5.0
configure: gromacs 4.5 was released, moved warning about devel version to gmx 5.0

MrTheodor/csg,junghans/csg,votca/csg,votca/csg,junghans/csg,junghans/csg,MrTheodor/csg,junghans/csg,MrTheodor/csg,votca/csg,junghans/csg,MrTheodor/csg,votca/csg,junghans/csg,MrTheodor/csg