horizontal vs. vertical padding

[Werner LEMBERG]

I try to provide a patch for issue #2185.  The given solution simply
reduces `Fingering.padding` from 0.5 to 0.3.  However, this affects
both horizontal and vertical padding, which is not what I want.  I
only want to change the horizontal padding, but it seems that we don't
have a property for that.  How could this be achieved with the
existing machinery?  Otherwise, would it be sensible to introduce new
properties `padding-x` and `padding-y` that get considered if
`padding` is not set?


    Werner