Fix Proc#arity.
Fix Proc#arity.

kachick/rubinius,jsyeo/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,kachick/rubinius,kachick/rubinius,jsyeo/rubinius,jsyeo/rubinius,jsyeo/rubinius,kachick/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius