add adjacent-hairpins property.
(apply define-internal-grob-property x))
`(
+
(accidental-grobs ,list? "Alist with (NOTENAME . GROBLIST) entries")
+ (adjacent-hairpins ,grob-list? "List of directly neighboring hairpins")
(after-line-breaking-callback ,procedure? "This procedure is called after line breaking. Its return value is ignored.")
(all-elements ,grob-list? "list of all grobs in this line. Its
function is to protect objects from being garbage collected.")