Make arguments like Context.GrobName accessible as symbol lists

input/regression/outside-staff-placement-directive.ly

-\version "2.17.5"
+\version "2.17.6"
 
 \header {
   texidoc = "@code{VerticalAxisGroup} grobs can place outside staff objects
 using one of the four directives shown below.
 "
 }
 
 
 \layout {
   ragged-right = ##t
   indent = 0.0
   \context {
     \Voice
     \remove "Ligature_bracket_engraver"
     \consists "Mensural_ligature_engraver"
   }
   \context {
     \Score
-    \override SpacingSpanner #'packed-spacing = ##t
-    \override PaperColumn #'keep-inside-line = ##f
+    \override SpacingSpanner.packed-spacing = ##t
+    \override PaperColumn.keep-inside-line = ##f
   }
 }
 
 music = \context Voice {
   \clef "petrucci-c4"
   \set Staff.printKeyCancellation = ##f
   \cadenzaOn % turn off bar lines
   \accidentalStyle forget
   \textLengthOn
 
@@ skipping 46 matching lines @@
 
   \[
     g1^\markup { "SS" }
     b
     \]
 
   \bar "|"
 }
 
 {
-  \override Staff.VerticalAxisGroup #'outside-staff-placement-directive =
+  \override Staff.VerticalAxisGroup.outside-staff-placement-directive =
     #'left-to-right-polite
   \music
 }
 {
-  \override Staff.VerticalAxisGroup #'outside-staff-placement-directive =
+  \override Staff.VerticalAxisGroup.outside-staff-placement-directive =
     #'left-to-right-greedy
   \music
 }
 {
-  \override Staff.VerticalAxisGroup #'outside-staff-placement-directive =
+  \override Staff.VerticalAxisGroup.outside-staff-placement-directive =
     #'right-to-left-polite
   \music
 }
 {
-  \override Staff.VerticalAxisGroup #'outside-staff-placement-directive =
+  \override Staff.VerticalAxisGroup.outside-staff-placement-directive =
     #'right-to-left-greedy
   \music
 }