libcc1: use unique_ptr more

This changes libcc1 to use unique_ptr in a few more places, removing
some manual memory management.

libcc1

	* libcp1.cc (struct libcp1) <connection, compilerp>: Use
	unique_ptr.
	(~libcp1): Remove.
	(libcp1_compile, libcp1_set_triplet_regexp)
	(libcp1_set_driver_filename): Update.
	* libcc1.cc (struct libcc1) <connection, compilerp>: Use
	unique_ptr.
	(~libcc1): Remove.
	(libcc1_set_triplet_regexp, libcc1_set_driver_filename)
	(libcc1_compile): Update.