Issue 4294: Functions to display rhythmic information of a grob
Convenient ways to return the musical position of a grob within
a score will be very helpful in debugging, among other uses.
This patch creates two Scheme functions which return the location
of a grob based on the associated paper column. In the case of
spanners, this is the column of the left bound.
(1) grob::rhythmic-location returns a pair consisting of measure-number
and measure-position;
(2) grob::when returns a moment representing the global timestep.