dwarf-reader: Canonicalize opaque enums and classes

dwarf-reader: Canonicalize opaque enums and classes

This issue was reported in bug https://sourceware.org/bugzilla/show_bug.cgi?id=27700.

When we construct an opaque type (triggered by the use of
--drop-private-types along with the --headers-dir option on abidw, for
instance) with get_opaque_version_of_type we forget to canonicalize
the resulting type.

Later, at abixml emitting time (for instance)
hash_as_canonical_type_or_constant would rightfully abort because the
type wasn't canonicalized.  We want all types (okay, modulo one
exception) in the system to be canonicalized.

This patch fixes the problem by canonicalizing opaque types.

	* src/abg-dwarf-reader.cc (build_ir_node_from_die): Canonicalize
	opaque enums and classes.
	* tests/data/test-read-dwarf/PR27700/include-dir/priv.h: New test
	header file.
	* tests/data/test-read-dwarf/PR27700/include-dir/pub.h: Likewise
	* tests/data/test-read-dwarf/PR27700/pub-incdir/inc.h: Likewise.
	* tests/data/test-read-dwarf/PR27700/test-PR27700.o: New binary
	input file.
	* tests/data/test-read-dwarf/PR27700/test-PR27700.abi: Reference
	abi file of the binary above.
	* tests/data/test-read-dwarf/PR27700/test-PR27700.c: Source file
	of the binary above.
	* tests/data/Makefile.am: Add the test material above to source
	distribution.
	* tests/test-read-dwarf.cc (InOutSpec::in_public_headers_path):
	Add new data member.
	(in_out_specs): Adjust to reflect the new data member in the
	InOutSpec type.  Add a new test input.
	(set_suppressions_from_headers): Define new static function.
	(test_task::perform): Use the content of the new
	InOutSpec::in_public_headers_path to construct and add
	"--headers-dir <headers-dir> --drop-private-types" to the options
	of the abidw program run.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>