Make arguments like Context.GrobName accessible as symbol lists

input/regression/tuplet-nest-broken.ly

 
-\version "2.16.0"
+\version "2.17.6"
 
 \header {
     texidoc = "Broken nested tuplets avoid each other correctly.
 "
 }
 
 \paper {
   ragged-right = ##t
   indent = 0.0
 }
 
 \score {
   \new Staff
   <<
     \relative c'' {
-      \override Score . Beam #'breakable = ##t
+      \override Score.Beam.breakable = ##t
 
       r2
 
       \times 4/3 {
         \times 2/3 { c8[ c c] }
         \times 2/3 { c8[ c c] }
         \times 2/3 { c8[ c c] }
       }
 
       \times 4/3 {
         \times 2/3 { a8[ a a] }
         \times 2/3 { a8[ a a] }
         \times 2/3 { a8[ a a] }
       }
 
-      \override TupletNumber #'text = #tuplet-number::calc-fraction-text
+      \override TupletNumber.text = #tuplet-number::calc-fraction-text
       \times 4/6 {
         \times 2/3 {
           a4 a a
         }
         \times 3/5 {
           a4 a a a a
         }
         a4
       }
       r2
     }
     { \repeat unfold 3 { s1 \break } }
   >>
   \layout {
     \context {
       \Voice \remove "Forbid_line_break_engraver"
     }
   }
 }