* dwarf2read.c (struct signatured_type): New member type.
	(struct attribute): Replace member signatured_type with signature.
	(DW_SIGNATURE): Replaces DW_SIGNATURE_TYPE.
	(read_call_site_scope): Call follow_die_ref instead of
	follow_die_ref_or_sig.
	(read_structure_type): Rewrite handling of signatured types.
	(read_enumeration_type): Ditto.
	(read_attribute_value): Update.
	(build_error_marker_type): New function.
	(lookup_die_type): Add assert.  Rewrite handling of signatured types.
	Don't call error for bad types, just build an error marker type.
	(dump_die_shallow): Update.
	(follow_die_sig_1): Renamed from follow_die_sig.
	Don't call error for bad types, instead return NULL.
	(follow_die_sig): New function.
	(get_signatured_type, get_DW_AT_signature_type): New functions.