new mechanism for hyphen determination

[eroux]

This should be a relatively small change, so I think we could do it even after rc1 if you agree. The idea is to make sure that when there is no hyphen, the spacing between the text of the two syllables of the same word is perfect. The means consists of several parts:

• make maximumspacewithoutdash 0 by default
• make sure that when outputing the space between two syllables of the same word when there is no hyphen needed, we use \kern and not hskip (in \gre@endofsyllable), so intersyllablespacenotes can have its plus and minus removed and become a dimen

I think this should be a relatively small change (around 15 lines). What do you think?

The next one I'm not 100% sure about and we can keep it for 5.0:

• introduce intersyllablespacenotesminus that will more or less correspond to the minus of intersyllablespacenotes but be handled by hand, the idea is that when the distance between the texts of the two syllables is less than this value (very small, around 0.3mm), we just make the notes a little bit closer, this will allow less hyphens to appear in scores

[eroux]

What remains for 5.0 is mainly linked with #923: it is to have a coherent rubber at the end of a syllable which is not the final syllable of a word. The particularity here is that this rubber has a minus set by the user but adapted to be at most the space between the text of the syllable and the text of the next syllable.