go spec: note re: append() not being implemented yet

R=rsc
CC=golang-dev
https://golang.org/cl/2761041

doc/go_spec.html

 <!-- title The Go Programming Language Specification -->
-<!-- subtitle Version of Oct 25, 2010 -->
+<!-- subtitle Version of Oct 26, 2010 -->
 
 <!--
 TODO
@@ -4557,6 +4557,10 @@ s2 := append(s1, 3, 5, 7)  // append multiple elements    s2 == []int{0, 0, 2, 3
 s3 := append(s2, s0...)    // append a slice              s3 == []int{0, 0, 2, 3, 5, 7, 0, 0}
 </pre>
 
+<p>
+<span class="alert">Note: <code>append</code> is not yet implemented.</span>
+</p>
+
 <p>
 The function <code>copy</code> copies slice elements from
 a source <code>src</code> to a destination <code>dst</code> and returns the
@@ -5228,6 +5232,7 @@ The following minimal alignment properties are guaranteed:
 <h2 id="Implementation_differences"><span class="alert">Implementation differences - TODO</span></h2>
 <ul>
 	<li><span class="alert">Implementation does not honor the restriction on goto statements and targets (no intervening declarations).</span></li>
+	<li><span class="alert">The <code>append</code> built-in function is not yet implemented.</span></li>
 	<li><span class="alert">Gccgo: Method expressions are partially implemented.</span></li>
 	<li><span class="alert">Gccgo: allows only one init() function per source file.</span></li>
 </ul>