gccgo does not yet implement _

OCL=34517
CL=34517

doc/go_spec.html

@@ -4398,6 +4398,7 @@ The following minimal alignment properties are guaranteed:
 <h2 id="Implementation_differences"><font color=red>Implementation differences - TODO</font></h2>
 <ul>
 	<li><font color=red>Implementation does not honor the restriction on goto statements and targets (no intervening declarations).</font></li>
+	<li><font color=red>Gccgo does not implement the blank identifier.</font></li>
 </ul>
 
 </div>