Fix prettyprinting for INTERSECTION:

core/prettyprint/prettyprint-tests.factor

@@ -334,5 +334,11 @@ PREDICATE: predicate-see-test < integer even? ;
     [ \ predicate-see-test see ] with-string-writer
 ] unit-test
 
+INTERSECTION: intersection-see-test sequence number ;
+
+[ "USING: math sequences ;\nIN: prettyprint.tests\nINTERSECTION: intersection-see-test sequence number ;\n" ] [
+    [ \ intersection-see-test see ] with-string-writer
+] unit-test
+
 [ ] [ \ compose see ] unit-test
 [ ] [ \ curry see ] unit-test

core/prettyprint/prettyprint.factor

@@ -7,8 +7,8 @@ vectors words prettyprint.backend prettyprint.sections
 prettyprint.config sorting splitting math.parser vocabs
 definitions effects classes.builtin classes.tuple io.files
 classes continuations hashtables classes.mixin classes.union
-classes.predicate classes.singleton combinators quotations
+classes.intersection classes.predicate classes.singleton
-sets ;
+combinators quotations sets ;
 
 : make-pprint ( obj quot -- block in use )
     [
@@ -238,6 +238,11 @@ M: union-class see-class*
     dup pprint-word
     members pprint-elements pprint-; block> ;
 
+M: intersection-class see-class*
+    <colon \ INTERSECTION: pprint-word
+    dup pprint-word
+    participants pprint-elements pprint-; block> ;
+
 M: mixin-class see-class*
     <block \ MIXIN: pprint-word
     dup pprint-word <block