[wwwdocs] Mention generic functions and explicit lambda templates in gcc-4.9/changes

[Adam Butcher <adam at jessamine dot co dot uk>]

Hi,

The following patch adds details of support for generic functions and 
the explicit template parameter extension for generic lambdas present in 
GCC 4.9.

OK to commit?

Cheers,
Adam

Index: htdocs/gcc-4.9/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.9/changes.html,v
retrieving revision 1.68
diff -u -r1.68 changes.html
--- htdocs/gcc-4.9/changes.html	22 Apr 2014 11:28:09 -0000	1.68
+++ htdocs/gcc-4.9/changes.html	29 Apr 2014 02:10:39 -0000
@@ -273,12 +273,37 @@
 </pre></blockquote>
   </li>
   <li>
-    G++ supports <a href="../projects/cxx1y.html">C++1y</a> 
polymorphic lambdas.
+    G++ supports <a href="../projects/cxx1y.html">C++1y</a>
+    generic (polymorphic) lambdas.
 <blockquote><pre>
 // a functional object that will increment any type
 auto incr = [](auto x) { return x++; };
 </pre></blockquote>
   </li>
+  <li>
+    As a GNU extension, G++ supports explicit template parameter
+    syntax for generic lambdas.  This can be combined in the expected
+    way with the standard <code>auto</code> syntax.
+<blockquote><pre>
+// a functional object that will add two like-type objects
+auto add = [] &lt;typename T&gt; (T a, T b) { return a + b; };
+</pre></blockquote>
+  </li>
+  <li>
+    G++ supports unconstrained <em>generic functions</em> as specified
+    by &sect;4.1.2 and &sect;5.1.1 of
+    <a 
href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3889.pdf";>
+    N3889: Concepts Lite Specification</a>.  Briefly,
+    <code>auto</code> may be used as a type-specifier in a parameter
+    declaration of any function declarator in order to introduce an
+    implicit function template parameter, akin to generic lambdas.
+<blockquote><pre>
+// the following two function declarations are equivalent
+auto incr(auto x) { return x++; }
+template &lt;typename T&gt;
+auto incr(T x) { return x++; }
+</pre></blockquote>
+  </li>
 </ul>

   <h4>Runtime Library (libstdc++)</h4>