Include Failure in smartmatch passthroughs

Only actual failure objects pass through.  You can match against Failure
as a literal type.  Presumably this can be distinguished by Failure.ACCEPTS.

Author: TimToady

S03-operators.pod

@@ -14,8 +14,8 @@ Synopsis 3: Perl 6 Operators
 
     Created: 8 Mar 2004
 
-    Last Modified: 23 Feb 2013
-    Version: 260
+    Last Modified: 6 Mar 2013
+    Version: 261
 
 =head1 Overview
 
@@ -3594,13 +3594,15 @@ as a default because the more specific types listed above it didn't match.
     Any       False     ~~ False match          (parsewarn on literal token)
     Any       Match     ~~ Successful match     (parsewarn on literal token)
     Any       Nil       ~~ Benign failure       (parsewarn on literal token)
+    Any       Failure   Failure type check      (okay, matches against type)
     Any       *         block signature match   block successfully binds to |$_
 
     Any       Callable:($)  item sub truth          X($_)
     Any       Callable:()   simple closure truth    X() (ignoring $_)
     Any       Bool      simple truth            X (treats Bool value as success/failure)
     Any       Match     match success           X (treats Match value as success)
     Any       Nil       benign failure          X (treats Nil value as failure)
+    Any       Failure   malign failure          X (passes Failure object through)
     Any       Numeric   numeric equality        +$_ == X
     Any       Stringy   string equality         ~$_ eq X
     Any       Whatever  always matches          True