empowered implied vol methods for displaced diffusion
better handling of evaluation dates which are not business dates
Merge branch 'master' of https://github.com/lballabio/quantlib
Merge branch 'master' of https://github.com/lballabio/quantlib
Merge branch 'master' of https://github.com/eehlers/quantlib
Merge branch 'master' of https://github.com/fametrano/quantlib