This adds deleter objects for various kinds of protocol pointers to
libcc1.  Existing specializations of argument_wrapper are then
replaced with a single specialization that handles all pointer types
via the appropriate deleter.  The result here is a bit nicer because
the argument_wrapper boilerplate code is completely shared, leaving
just the memory-management detail to the particular specializations.

libcc1

	* rpc.hh (struct deleter): New template class and
	specializations.
	(argument_wrapper): Remove specializations.  Add specialization
	for any pointer type.