Let Ferneyhough hairpins support al niente circles
Also providing extended regtests and changes.tely
This patch does as the title says, though, it does not deal with the possibilty of broken hairpins, this is another issue. Nevertheless, because per default after-line-breaking for Hairpins is set to ly:spanner::kill-zero-spanned-time, we have to look at the break status of the Hairpin, if a decrescendo ends at first note of a new line. We ensure to print a circled tip at the relevant part of the Hairpin.
Closes #3357 (closed)