* lily/include/paper-line.hh (class Paper_line): New member

* lily/include/paper-line.hh (class Paper_line): New member
var penalty_.

* lily/system.cc (get_line): Initialise Paper_line with
page-penalty's from original grobs.

* scm/define-music-properties.scm (all-music-properties): Add
page-penalty.

* scm/define-grob-properties.scm (all-grob-descriptions): Idem.

* lily/score-engraver.cc (try_music): Handle page-penalty.

* ly/declarations-init.ly (pagebreak, noPagebreak): New command.