Don't store tree's hidden children in a separate array

Just mark hidden trees as such, and skip them when
pretty-printing a tree

spec/runtime/languages/json/errors.txt

@@ -17,24 +17,24 @@ recovers from errors inside arrays
 ==========================================
 [1, , 2]
 ---
-(value (array
+(array
     (number)
     (ERROR <EOF>)
-    (number)))
+    (number))
 
 ==========================================
 recovers from errors inside objects
 ==========================================
 { "key1": 1, oops }
 ---
-(value (object (string) (number) (ERROR 'o')))
+(object (string) (number) (ERROR 'o'))
 
 ==========================================
 recovers from errors inside nested objects
 ==========================================
 { "key1": { "key2": 1, 2 }, [, "key3": 3 }
 ---
-(value (object
+(object
     (string) (object (string) (number) (ERROR '2'))
     (ERROR '[')
-    (string) (number)))
+    (string) (number))

spec/runtime/languages/json/main.txt

@@ -3,14 +3,14 @@ parses floating point numbers
 =============================
 3.14
 ---
-(value (number))
+(number)
 
 ===================
 parses empty arrays
 ===================
 []
 ---
-(value (array))
+(array)
 
 ===================
 parses arrays
@@ -23,19 +23,19 @@ parses arrays
     { "stuff": "good" }
 ]
 ---
-(value (array
+(array
     (number)
     (null)
     (true)
     (false)
-    (object (string) (string))))
+    (object (string) (string)))
 
 ====================
 parses empty objects
 ====================
 {}
 ---
-(value (object))
+(object)
 
 ===================
 parses long objects
@@ -45,8 +45,7 @@ parses long objects
 	"key2": 1
 }
 ---
-(value (object
+(object
 	(string) (string)
-	(string) (number)
-))
+	(string) (number))