* rs6000-tdep.c: Use the modern gdbarch methods for handling the

* rs6000-tdep.c: Use the modern gdbarch methods for handling the
register set, so our regcache isn't declared "legacy" and our E500
pseudoregister read and write functions aren't ignored.
(rs6000_register_byte, rs6000_register_raw_size,
rs6000_register_virtual_type, rs6000_register_convertible,
rs6000_register_convert_to_virtual,
rs6000_register_convert_to_raw): Deleted.
(rs6000_register_type, rs6000_convert_register_p,
rs6000_register_to_value, rs6000_value_to_register): New
functions.
(rs6000_gdbarch_init): Don't register
gdbarch_deprecated_register_size,
gdbarch_deprecated_register_bytes,
gdbarch_deprecated_register_byte,
gdbarch_deprecated_register_raw_size,
gdbarch_deprecated_register_virtual_type,
gdbarch_deprecated_register_convertible,
gdbarch_deprecated_register_convert_to_virtual, or
gdbarch_deprecated_register_convert_to_raw methods.  Instead,
register gdbarch_register_type, gdbarch_convert_register_p,
gdbarch_register_to_value, and gdbarch_value_to_register methods.