"efuse not defined" bug in 1.6.5 (more or less solved)

i lack experience with that level of arduino ide so any more details would be appreciated, ie what folders etc.

it is amazing that team ardu allows such goofs to persist with something as popular as ng (coming soon to a theater near you: The Chip That Wouldnt Die!!!). not interesting to ivory tower residents who prefer bleeding edge but lucky for the other 99% who appreciate old but cheap&proven tech.