Make arguments like Context.GrobName accessible as symbol lists

input/regression/bar-number-volta-repeat.ly

-\version "2.16.0"
+\version "2.17.6"
 
 \header {
   texidoc = "Bar numbers can automatically reset at volta repeats.
 "
 }
 
 musicWithBarNumberCheck =
 #(define-music-function (parser location n)
   (integer?)
 #{
   \relative c' {
-    \override Score.BarNumber #'break-visibility = #'#(#t #t #t)
+    \override Score.BarNumber.break-visibility = #'#(#t #t #t)
     \repeat volta 28 {
      c1 |
      c |
      c |
     }
     \alternative {
         << { c \barNumberCheck #n c } \\ { e e } >>
       {
         c \barNumberCheck #n c |
       }
       {
         c \barNumberCheck #n c |
       }
     }
     c c
   }
 #})
 
 {
   \set Score . alternativeNumberingStyle = #'numbers
   \musicWithBarNumberCheck #5
   \musicWithBarNumberCheck #12
 }
 { \set Score . alternativeNumberingStyle = #'numbers-with-letters
   \musicWithBarNumberCheck #5
   \musicWithBarNumberCheck #12
 }