Make arguments like Context.GrobName accessible as symbol lists

Documentation/snippets/adding-drum-parts.ly

 %% DO NOT EDIT this file manually; it is automatically
 %% generated from LSR http://lsr.dsi.unimi.it
 %% Make any changes in LSR itself, or in Documentation/snippets/new/ ,
 %% and then run scripts/auxiliar/makelsr.py
 %%
 %% This file is in the public domain.
-\version "2.17.5"
+\version "2.17.6"
 
 \header {
   lsrtags = "percussion, preparing-parts, really-simple, rhythms, specific-notation"
 
   texidoc = "
 Using the powerful pre-configured tools such as the @code{\\drummode}
 function and the @code{DrumStaff} context, inputting drum parts is
 quite easy: drums are placed at their own staff positions (with a
 special clef symbol) and have note heads according to the drum.
 Attaching an extra symbol to the drum or restricting the number of
 lines is possible.
 
 "
   doctitle = "Adding drum parts"
 } % begin verbatim
 
 
 drh = \drummode { cymc4.^"crash" hhc16^"h.h." hh hhc8 hho hhc8 hh16 hh hhc4 r4 r2 }
 drl = \drummode { bd4 sn8 bd bd4 << bd ss >>  bd8 tommh tommh bd toml toml bd tomfh16 tomfh }
 timb = \drummode { timh4 ssh timl8 ssh r timh r4 ssh8 timl r4 cb8 cb }
 
 \score {
   <<
     \new DrumStaff \with {
       drumStyleTable = #timbales-style
-      \override StaffSymbol line-count = #2
-      \override BarLine bar-extent = #'(-1 . 1)
+      \override StaffSymbol.line-count = #2
+      \override BarLine.bar-extent = #'(-1 . 1)
     } <<
       \set Staff.instrumentName = #"timbales"
       \timb
     >>
     \new DrumStaff <<
       \set Staff.instrumentName = #"drums"
       \new DrumVoice { \stemUp \drh }
       \new DrumVoice { \stemDown \drl }
     >>
   >>
   \layout { }
   \midi {
     \tempo 4 = 120
   }
 }