Loose-lines honor padding between systems (issue4553060)

[tdanielsmusic]

Looks ok to me, although I haven't tested it.
Need Joe's LGTM to push.


http://codereview.appspot.com/4553060/diff/7001/input/regression/page-spacing-nonstaff-lines-between-2.ly
File input/regression/page-spacing-nonstaff-lines-between-2.ly (right):

http://codereview.appspot.com/4553060/diff/7001/input/regression/page-spacing-nonstaff-lines-between-2.ly#newcode1
input/regression/page-spacing-nonstaff-lines-between-2.ly:1: \version
"2.13.42"
2.13.62

http://codereview.appspot.com/4553060/diff/7001/lily/include/page-layout-problem.hh
File lily/include/page-layout-problem.hh (right):

http://codereview.appspot.com/4553060/diff/7001/lily/include/page-layout-problem.hh#newcode64
lily/include/page-layout-problem.hh:64: Element (vector<Grob*> const& a,
vector<Real> const& o, Real p)
use pad here too for consistency?

http://codereview.appspot.com/4553060/diff/7001/lily/page-layout-problem.cc
File lily/page-layout-problem.cc (right):

http://codereview.appspot.com/4553060/diff/7001/lily/page-layout-problem.cc#newcode545
lily/page-layout-problem.cc:545: // distance to the final line in the
preceeding system,
preceding

http://codereview.appspot.com/4553060/