haha. It never crossed my mind if there were a tool for that, I just read that they need to be converted and went renaming.
It was just like 5 or so directories and the mission file(s), so it wasn't that much of a chore.
I seem to remember got rid of those errors by manually renaming every directory / file in arma-directory to lowercase
like, Dta becomes dta, Expansion = expansion.