Remove the IND_OLDGEN and IND_OLDGEN_PERM closure types

Remove the IND_OLDGEN and IND_OLDGEN_PERM closure types
These are no longer used: once upon a time they used to have different
layout from IND and IND_PERM respectively, but that is no longer the
case since we changed the remembered set to be an array of addresses
instead of a linked list of closures.