Re: Suppress continuing LyricHyphen under grace note at start of line (issue4313047)

[tdanielsmusic]

Patch set 3 follows up on Neil's suggestion to use
the kill-zero-spanned-time callback.  This patch
removes the changes in Patch set 1 (which was pushed)
and implements this alternative fix.  This is both
simpler and permits the behaviour to be changed with
an override.

Regtests run clean.

@Neil: hope this change to kill-zero-spanned-time ()
to ignore grace notes is what you intended by "a
minor tweak".  It seems to have no side-effects.

http://codereview.appspot.com/4313047/