Avoid using Skyline_pair::insert. (issue 554000043 by hanwenn@gmail.com)

[jonas . hahnfeld]

https://codereview.appspot.com/554000043/diff/549990043/lily/align-interface.cc
File lily/align-interface.cc (right):

https://codereview.appspot.com/554000043/diff/549990043/lily/align-interface.cc#newcode90
lily/align-interface.cc:90: Real offset = g->relative_coordinate
(other_common, other_axis (a));
Is this code intentionally moving into if (skys) ?

https://codereview.appspot.com/554000043/