Adjust operators' classification and xref them

Author: stoned

doc/Type/Callable.pod6

@@ -30,7 +30,8 @@ of such a container is C<Callable>.
 
     method CALL-ME(Callable:D $self: |arguments)
 
-This method is required for postfix:«( )» and postfix:«.( )». It's what makes
+This method is required for L«C<( )> postcircumfix operator|/language/operators#postcircumfix_(_)»
+and L«C<.( )> postcircumfix operator|/language/operators#index-entry-.(_)». It's what makes
 an object actually call-able and needs to be overloaded to let a given object
 act like a routine. If the object needs to be stored in a C<&>-sigiled
 container, is has to implement Callable.