rework the construction of reverse ecode mappings with regard to FF_*
rework the construction of reverse ecode mappings with regard to FF_*

ProfessorKaos64/python-evdev,ProfessorKaos64/python-evdev,gvalkov/python-evdev,ProfessorKaos64/python-evdev,gvalkov/python-evdev,gcd0318/python-evdev,gcd0318/python-evdev,gcd0318/python-evdev