[perl #61172] hash becomes string or int

[Patrick R. Michaud via RT]

Now fixed in r35397:

  $ ./parrot perl6.pbc
  > sub foo(%h?) { { a => 1, %h }.perl.say; };
  > foo( { b => 2 } );
  {"a" => 1, "b" => 2}
  > foo( { } );
  {"a" => 1}
  > foo( );
  {"a" => 1}
  >

We need tests for optional array and hash parameters in the test suite,
so assigning ticket to moritz.  Thanks!

Pm