src/Pure/General/pretty.ML

   val keyword2: string -> T
   val text: string -> T list
   val paragraph: T list -> T
   val para: string -> T
   val quote: T -> T
-  val backquote: T -> T
   val cartouche: T -> T
   val separate: string -> T list -> T list
   val commas: T list -> T list
   val enclose: string -> string -> T list -> T
   val enum: string -> string -> string -> T list -> T

 val text = breaks o map str o Symbol.explode_words;
 val paragraph = markup Markup.paragraph;
 val para = paragraph o text;
 
 fun quote prt = blk (1, [str "\"", prt, str "\""]);
-fun backquote prt = blk (1, [str "`", prt, str "`"]);
 fun cartouche prt = blk (1, [str "\\<open>", prt, str "\\<close>"]);
 
 fun separate sep prts =
   flat (Library.separate [str sep, brk 1] (map single prts));