libdpkg: Add missing command_shell to version script

lib/dpkg/libdpkg.Versions

@@ -102,6 +102,7 @@ LIBDPKG_PRIVATE {
 	command_add_argv;
 	command_add_args;
 	command_exec;
+	command_shell;
 	command_destroy;
 
 	setcloexec;