Add non-breaking space inside French quotes

For some reason, preg_replace("/\s([»])/", ' $1', 'foo « bar »') seems to also replace the « character and I am not sure sure why. Because of this, preg_replace("/\s([\!\?\:;»])/", ' $1', $t) wouldn't do what I wanted.
So I had to work around this by using a separate preg_replace() without [].

I don't know if it's OK, since it is an old unmaintained library?

Right, I prefer not to touch it unless it is doing something obviously wrong.

If we are going to change it, then we should add some tests to make sure that we are not getting some undesired behavior. Can you provide some test cases: strings before and after applying the typogrify filter? Better yet, could you add them to the data provider in the automated test?

I am not sure that spaceToNbsp() is the right place to make this change. It does not match the purpose of that function, as described in its doc block.

Looking at the code (but not testing) it seems that the change to i18nQuotes() will insert the non-breaking space in some cases that currently do not get any sort of space. That seems like an unwanted side effect.