Allows lyrics to slide under TimeSignature when OctaveEight present. (issue 6201068)

[janek . lilypond]

http://codereview.appspot.com/6201068/diff/1/lily/pure-from-neighbor-engraver.cc
File lily/pure-from-neighbor-engraver.cc (right):

http://codereview.appspot.com/6201068/diff/1/lily/pure-from-neighbor-engraver.cc#newcode56
lily/pure-from-neighbor-engraver.cc:56: in_same_column (Grob *g1, Grob
*g2)
That's problably the most stupid question ever, but why this doesn't it
begin with Pure_from_neighbor_engraver:: ?  I don't see it being
special.

http://codereview.appspot.com/6201068/diff/1/lily/pure-from-neighbor-engraver.cc#newcode119
lily/pure-from-neighbor-engraver.cc:119:
Pointer_group_interface::add_grob
(need_pure_heights_from_neighbors[pos[j]][k], ly_symbol2scm
("neighbors"), pure_relevants_[i]);
could you reduce line width, please?  This one is way over regular 80
chars limit.

http://codereview.appspot.com/6201068/