This changes libcc1 to use the 'deleter' template in a few more
places. The template and basic specializations are moved to a new
header, then some unmarshall functions are changed to use this code.
This change avoids the need to repeat cleanup code in the
unmarshallers.
libcc1
* rpc.hh (deleter): Move template and some specializations to
deleter.hh.
(argument_wrapper<const T *>): Use cc1_plugin::unique_ptr.
* marshall.cc (cc1_plugin::unmarshall): Use
cc1_plugin::unique_ptr.
* marshall-cp.hh (deleter): New specializations.
(unmarshall): Use cc1_plugin::unique_ptr.
* deleter.hh: New file.
