[gentium] LGR: Missing ligature s-boundarychar

[Karl Berry]

    I have therefore used a the following command  for testing:

Thanks Ralf. You made it easy. I presume the same should be applied to
lgr-gentiumplus-italic.tfm, right? Do any of other tfms need to be
touched for your use? I'm inclined to leave everything else alone.

At any rate, I tweaked the doc and think I've got a new package ready to
upload, if there's nothing else ... --thanks, karl.