Simplifies value extraction in `can-override`.
Simplifies value extraction in `can-override`.

We now pass wrapped properties only so there's no need anymore to
do an array check.

vlajos/clean-css,jakubpawlowicz/clean-css,stuht/clean-css,MartyIX/clean-css,scottgonzalez/clean-css,island205/clean-css,GerHobbelt/clean-css,shelsonjava/clean-css,yomed/clean-css