Docs: update for constification

Broken-by: ecb371298c

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 3691b8ba6d2061e0af49e310f106ca23322150c5..812924ac822473492a48feb8ef0ed43b9beb4835 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -35384,8 +35384,10 @@ discussed below.
 .vitem &*header_line&~*header_last*&
 A pointer to the last of the header lines.
 
-.vitem &*uschar&~*headers_charset*&
+.new
+.vitem &*const&~uschar&~*headers_charset*&
 The value of the &%headers_charset%& configuration option.
+.wen
 
 .vitem &*BOOL&~host_checking*&
 This variable is TRUE during a host checking session that is initiated by the