regexp: Fix / escape in regexp. Fixes validators test.

basis/regexp/prettyprint/prettyprint.factor

@@ -7,7 +7,7 @@ IN: regexp.prettyprint
 M: regexp pprint*
     [
         [
-            [ raw>> "R/ " % % "/" % ]
+            [ raw>> "\\/" "\\\\/" replace "R/ " % % "/" % ]
             [ options>> options>string % ] bi
         ] "" make
     ] keep present-text ;

basis/regexp/regexp.factor

@@ -211,7 +211,7 @@ PRIVATE>
     dup still-parsing-line? [ (parse-raw) ] [ drop f ] if ;
 
 : parse-regexp ( accum -- accum )
-    lexer get [ take-until ] [ parse-noblank-token ] bi
+    lexer get [ take-until "\\/" "/" replace ] [ parse-noblank-token ] bi
     <optioned-regexp> compile-next-match suffix! ;
 
 PRIVATE>