src/Pure/General/markup.scala

   val NUM = "num"
   val FLOAT = "float"
   val XNUM = "xnum"
   val XSTR = "xstr"
   val LITERAL = "literal"
+  val INNER_STRING = "inner_string"
   val INNER_COMMENT = "inner_comment"
 
   val TOKEN_RANGE = "token_range"
 
   val SORT = "sort"