Mention unsupported GCC duplicate-definition-with-inline extension.

Also, link users manual from the main web page.

llvm-svn: 72878

clang/docs/UsersManual.html

@@ -600,6 +600,12 @@ in structures.  This is for a few of reasons: one, it is tricky
 to implement, two, the extension is completely undocumented, and three, the
 extension appears to be very rarely used.</p>
 
+<p>clang does not support duplicate definitions of a function where one is
+inline. This complicates clients of the AST which normally can expect there is
+at most one definition for each function. Source code using this feature should
+be changed to define the inline and out-of-line definitions in separate
+translation units.</p>
+
 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
 <h3 id="c_ms">Microsoft extensions</h3>
 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->

clang/www/menu.html.incl

@@ -8,6 +8,11 @@
     <a href="/index.html">About</a>
     <a href="/features.html">Features</a>
     <a href="/comparison.html">Comparisons</a>
+    <a href="/docs/UsersManual.html">Users Manual</a>
+  </div>
+
+  <div class="submenu">
+    <label>Clang Development</label>
     <a href="/get_started.html">Get&nbsp;Started</a>
     <a href="/get_involved.html">Get&nbsp;Involved</a>
     <a href="/OpenProjects.html">Open&nbsp;Projects</a>