[luatex] Hyphenation on ligatures

[Igor Liferenko]

What is curious: if we comment out \lccode in the example, pdftex
fails with this (as it should):

(./test.tex
! Not a letter.
l.5 \hyphenation{'
                  '-aa-''}
?

But luatex happily processes the file (giving the same output as
pdftex did before commenting out \lccode).