IR 3.2.111 doesn't mention 'numbered style

[Mark Polesky]

IR 3.2.111 time-signature-interface doesn't 
mention the 'numbered style. Also, on a more
general level, the default description for 
the "style" property in IR 3 is the same 
for a lot of different grobs, IIRC:

This setting determines in what style a grob 
is typeset.  Valid choices depend on the 
stencil callback reading this property.

It would be nice to see more specific entries
like:

IR 3.2.64 note-head-interface:
'style
   The note-head style. Valid choices are 
   default, baroque, neomensural, mensural,
   petrucci, harmonic, harmonic-black, 
   harmonic-mixed, diamond, cross, xcircle,
   triangle, slash. Also see NR B.7.

IR 3.1.114 time-signature:
'style
   The time-signature style. Valid choices are
   C, neomensural, mensural, single-digit and
   numbered. Also see IR 3.2.111

- Mark