[wwwdocs] Document recent libstdc++ changes

[Jonathan Wakely]

Committed to CVS.



Index: htdocs/gcc-9/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-9/changes.html,v
retrieving revision 1.49
diff -u -r1.49 changes.html
--- htdocs/gcc-9/changes.html	28 Feb 2019 21:49:05 -0000	1.49
+++ htdocs/gcc-9/changes.html	6 Mar 2019 10:20:44 -0000
@@ -213,15 +213,35 @@
 
 <h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
 <ul>
+  <li>Improved experimental support for C++17,
+      including <code>&lt;memory_resource&gt;</code>.
+  </li>
   <li>Improved experimental support for C++2a,
-      including type traits <code>std::remove_cvref</code>,
-      <code>std::is_nothrow_convertible</code>, and
-      <code>std::type_identity</code>,
-      and headers <code>&lt;bit&gt;</code> and <code>&lt;version&gt;</code>.
+      including:
+      <ul>
+      <li>Type traits <code>std::remove_cvref</code>,
+        <code>std::unwrap_reference</code>, <code>std::unwrap_decay_ref</code>,
+        <code>std::is_nothrow_convertible</code>, and
+        <code>std::type_identity</code>;</li>.
+      <li>Headers <code>&lt;bit&gt;</code> and
+        <code>&lt;version&gt;</code>.</li>
+      <li>Uniform container erasure (<code>std::erase_if</code>).</li>
+      <li><code>contains</code> member of maps and sets.</li>
+      <li>String prefix and suffix checking (<code>starts_with</code>,
+        <code>ends_with</code>).</li>
+      <li>Functions <code>std::midpoint</code> and <code>lerp</code> for
+        interpolation.</li>
+      <li>Uses-allocator construction utilities.</li>
+      <li><code>std::pmr::polymorphic_allocator&lt;std::byte&gt;</code>.</li>
+      <li>Library support for <code>char8_t</code> type.</li>
+      <li>Destroying <code>delete</code>.</li>
+      <li><code>std::is_constant_evaluated()</code> function.</li>
+      </ul>
   </li>
   <li>Support for opening file streams with wide character paths on Windows</li>
   <li>Incomplete support for the C++17 Filesystem library and the Filesystem
       TS on Windows.</li>
+  <li>Incomplete, experimental support for the Networking TS.</li>
 </ul>
 
 <h3 id="d">D</h3>