It offers a command line version of what to do. Not sure how to proceed on Windows. Does poedit offer merging of files? I guess it does, but I don't know how. Some googling revealed that there must be a "update from PO file" option. Find it and use that, I guess.
There is a way. Open ro.po file using poedit (4.7 translation) Now click Update from POT template in menu and select .pot file from 5.x Safe updated file as something-something.po
Do this for all instances of 5.x .pot templates