Add support for pre/post scan hooks.
Add support for pre/post scan hooks.

gjcarneiro/pybindgen,ftalbrecht/pybindgen,gjcarneiro/pybindgen,gjcarneiro/pybindgen,ftalbrecht/pybindgen,cawka/pybindgen-old,cawka/pybindgen-old,ftalbrecht/pybindgen,cawka/pybindgen-old,gjcarneiro/pybindgen,ftalbrecht/pybindgen,cawka/pybindgen-old