Make Metamodel::EnumHOW consumer of ::Composing

Also relax sigature on default .compose, as it's not being checked
anyway, so just blindly eat any nameds by default

src/Perl6/Metamodel/Composing.nqp

@@ -6,7 +6,7 @@ role Perl6::Metamodel::Composing {
     has int $!composed;
 
     # Null operation, if the consumer doesn't supply a "compose" of its own
-    method compose($XXX?, :$compiler_services) { $!composed := 1 }
+    method compose($XXX?, *%_) { $!composed := 1 }
 
     method set_composed($XXX?) { $!composed := 1 }
     method is_composed($XXX?)  { $!composed      }

src/Perl6/Metamodel/EnumHOW.nqp

@@ -5,6 +5,7 @@
 class Perl6::Metamodel::EnumHOW
     does Perl6::Metamodel::Naming
     does Perl6::Metamodel::Documenting
+    does Perl6::Metamodel::Composing
     does Perl6::Metamodel::LanguageRevision
     does Perl6::Metamodel::Stashing
     does Perl6::Metamodel::AttributeContainer
@@ -37,9 +38,6 @@ class Perl6::Metamodel::EnumHOW
     has $!role;
     has int $!roled;
 
-    # Are we composed yet?
-    has $!composed;
-
     # Exportation callback for enum symbols, if any.
     has $!export_callback;
 
@@ -168,9 +166,9 @@ class Perl6::Metamodel::EnumHOW
         self.create_BUILDPLAN($obj);
 
         # Compose the representation.
-        unless $!composed {
+        unless self.is_composed {
             self.compose_repr($obj);
-            $!composed := 1;
+            self.set_composed;
         }
 
 #?if !moar
@@ -200,10 +198,6 @@ class Perl6::Metamodel::EnumHOW
         $!role
     }
 
-    method is_composed($obj) {
-        $!composed
-    }
-
     method role_typecheck_list($obj) {
         @!role_typecheck_list
     }