* src/abg-ir.h (location::{operator==, operator<})
(decl_base::operator==, scope_decl::operator==)
(type_base::operator==, struct type_shared_ptr_equal)
(type_decl::operator==, scope_type::operator==)
(qualified_type_def::operator==, class pointer_type_def): New
declarations..
* src/abg-ir.cc (decl_base::operator==, scope_decl::operator==)
(type_base::operator==, type_decl::operator==)
(scope_type_decl::operator==, namespace_decl::operator==)
(qualified_type_def::operator==)
(pointer_type_def::pointer_type_def, pointer_type_def::operator==)
(pointer_type_def::get_pointed_to_type)
(pointer_type_def::~pointer_type_def): New definitions.
* src/abg-reader.cc (handle_pointer_type_def): New definition.
(read_input): Handle pointer-type-def
elements.
* src/abg-writer.cc (type_shared_ptr_map): Make this map use the
use type_shared_ptr_equal predicate.
(write_pointer_type_def): New definition.
(write_decl): Improve logic. Support serializing a pointer to
pointer_type_def.
* tests/data/test-read-write/test4.xml: New test input file.
* tests/Makefile.am: Add tests/data/test-read-write/test4.xml to
the build system.
* tests/test-read-write.cc: (De)serialize the new test file.
