Fully account for anonymous-ness of scopes when comparing decl names

Fully account for anonymous-ness of scopes when comparing decl names

When comparing internal decl names (as part of decl comparison), we
need to take into account the fact that a given decl might be
anonymous and that it might have anonymous scopes in its tree of
containing scopes.

For instance, "__anonymous_struct__1::foo" and
"__anonymous_struct__2::foo" are considered equivalent.

So are "__anonymous_struct__1::foo::__anonymous_struct__2::bar" and
"__anonymous_struct__10::foo::__anonymous_struct__11::bar".

But "__anonymous_struct__1::bar::__anonymous_struct__2::baz" and
"__anonymous_struct__10::foo::__anonymous_struct__11::bar" are not.

This patch introduces the function tools_utils::decl_names_equal that
compares fully qualified names by taking into account anonymous
component names.

That function is thus used in the equals() function overload for
decl_base types.  Because tools_utils::decl_names_equal compares strings the
usual way (character by character) it's slower than comparing
instances of interned_string in a O(1) time.  So the patch carefully
tries to use tools_utils::decl_names_equal sparringly; that is, it
uses it only when we are looking at decls that have some anonymous
scope.  That way, we use the fast interned_string comparison most of
the time.  By doing this, we barely see any performance degradation
while running abidw --noout on a full blown vmlinux binary.

	* include/abg-ir.h (decl_base::{get_has_anonymous_parent,
	set_has_anonymous_parent,
	get_is_anonymous_or_has_anonymous_parent}): Declare new member
	functions.
	* src/abg-ir.cc (decl_base::priv::has_anonymous_parent_): Define
	new data member.
	(decl_base::priv): Initialize the new data member.
	(decl_base::{get_has_anonymous_parent, set_has_anonymous_parent,
	get_is_anonymous_or_has_anonymous_parent}): Define new member
	functions.
	(equals): In the overload for decl_base, use the new
	decl_names_equal for decls that have anonymous scopes.
	(scope_decl::add_member_decl): Propagate the
	decl_base::has_anonymous_parent_ property.
	* include/abg-tools-utils.h
	(get_anonymous_struct_internal_name_prefix)
	(get_anonymous_union_internal_name_prefix)
	(get_anonymous_enum_internal_name_prefix, decl_names_equal):
	Declare new functions.
	* src/abg-comp-filter.cc (has_harmless_name_change): Handle the
	case where the name change is actually from an anonymous name to
	another one, using the new decl_names_equal function.
	* src/abg-dwarf-reader.cc
	(get_internal_anonymous_die_prefix_name): Renamed
	get_internal_anonynous_die_base_name into this.  Use the new
	get_anonymous_{struct, union, enum}_internal_name_prefix functions
	here.
	(get_internal_anonymous_die_name, die_qualified_type_name)
	(build_enum_type, add_or_update_class_type)
	(add_or_update_union_type): Adjust.
	* src/abg-tools-utils.cc (get_anonymous_struct_internal_name_prefix)
	(get_anonymous_union_internal_name_prefix)
	(get_anonymous_enum_internal_name_prefix, decl_names_equal):
	Define new functions.
	* tests/test-tools-utils.cc: New test file.
	* tests/Makefile.am: Add new runtesttoolsutils test, built from
	test-tools-utils.cc.
	* tests/data/test-diff-dwarf/test46-rust-report-0.txt: Adjust.
	* tests/data/test-diff-pkg/spice-server-0.12.4-19.el7.x86_64-0.12.8-1.el7.x86_64-report-3.txt:
	Likewise.
	* tests/data/test-read-dwarf/PR22122-libftdc.so.abi: Likewise.

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