Make | flattening work on pairs, which flatten as named arguments.

docs/ChangeLog

@@ -15,6 +15,7 @@ New in 2012.06
 + require with argument list
 + compile time errors in loaded modules now show a module loading backtrace
 + improved list and .map handling
++ can now use | to flatten a pair into an argument list as a named argument
 
 New in 2012.05
 + meta ops //=, ||= and &&= now short-circuit properly

src/core/Enum.pm

@@ -36,6 +36,9 @@ my class Enum does Associative {
     method at_key($key) {
         $key eq $!key ?? $!value !! Mu
     }
+
+    method FLATTENABLE_LIST() { nqp::list() }
+    method FLATTENABLE_HASH() { nqp::hash($!key, $!value) }
 }
 
 multi sub infix:<eqv>(Enum:D $a, Enum:D $b) {