missing Python3 compat + RISC OS 5

gradint-build/Makefile

gradint-build/src/booktime.py

gradint-build/src/filescan.py

gradint-build/src/frontend.py

gradint-build/src/lessonplan.py

gradint-build/src/loop.py

gradint-build/src/makeevent.py

gradint-build/src/play.py

gradint-build/src/recording.py

gradint-build/src/sequence.py

gradint-build/src/synth.py

gradint-build/src/system.py

gradint-build/src/top.py

gradint-build/src/users.py

gradint-build/thindown.py