[cage] Remove PMCProxy.mark and .destroy.
[cage] Remove PMCProxy.mark and .destroy.

PMCProxy inherited from Class and doesn't have additional ATTRibutes. Which means
PMCProxy.mark and .destroy should be exactly the same as Class'.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@40077 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot