Update Makefile to more recent version
Update Makefile to more recent version

Copied over from a more up to date Sphinx project. Not sure how one goes
about updating the Makefile in a more official way.

AnthonyTruchet/breathe,RR2DO2/breathe,kirbyfan64/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,RR2DO2/breathe