Make list of `non-staff lines' easier to find in IR.

Linking from the NR to the Axis_group_engraver IR entry
directs the reader to the list of staff contexts and
`non-staff line' contexts.

diff --git a/Documentation/notation/spacing.itely b/Documentation/notation/spacing.itely
index c88f6b2c1bf87986817c90e40bcd5ec927eada04..b2da6c861b26921356eda5d4693a56ebcffe418a 100644 (file)
--- a/Documentation/notation/spacing.itely
+++ b/Documentation/notation/spacing.itely
@@ -2285,8 +2285,8 @@ Internals Reference:
 @emph{Non-staff lines} (such as @code{Lyrics}, @code{ChordNames},
 etc.) are contexts whose layout objects are engraved like staves
 (i.e. in horizontal lines within systems).  Specifically,
-non-staff lines are non-staff contexts that create the
-@code{VerticalAxisGroup} layout object.
+non-staff lines are non-staff contexts that contain the
+@rinternals{Axis_group_engraver}.
 
 The following properties affect the spacing of non-staff lines: