libdpkg: Add missing symbols to the version script

lib/dpkg/libdpkg.map

@@ -112,7 +112,7 @@ LIBDPKG_PRIVATE {
 	# Buffer I/O functions
 	fd_read;
 	fd_write;
-	buffer_hash;
+	buffer_filter;
 	buffer_skip_*;
 	buffer_copy_*;
 
@@ -205,6 +205,8 @@ LIBDPKG_PRIVATE {
 	dpkg_arch_save_list;
 
 	# Package struct handling
+	pkgset_blank;
+	pkgset_link_pkg;
 	pkgset_installed_instances;
 	pkg_blank;
 	pkgbin_blank;