This commit covers the most important one.
* src/autofit/afmodule.c (af_property_set): Handle `warping',
`darkening-parameters', and `no-stem-darkening'.
* src/cff/cffdrivr.c (cff_property_set): Handle
`darkening-parameters', `hinting-engine', and `no-stem-darkening'.
* src/truetype/ttdriver.c (tt_property_set): Handle
`interpreter-version'.