8282668: HotSpot Style Guide should permit unrestricted unions

Reviewed-by: dholmes, dcubed, tschatzl, kvn

doc/hotspot-style.html

@@ -428,6 +428,7 @@ <h3 id="additional-permitted-features">Additional Permitted Features</h3>
 <li><p><code>final</code> virtual specifiers for classes and virtual functions (<a href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2928.htm">n2928</a>), (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3206.htm">n3206</a>), (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3272.htm">n3272</a>)</p></li>
 <li><p><code>override</code> virtual specifiers for virtual functions (<a href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2928.htm">n2928</a>), (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3206.htm">n3206</a>), (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3272.htm">n3272</a>)</p></li>
 <li><p>Range-based <code>for</code> loops (<a href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2930.html">n2930</a>) (<a href="https://en.cppreference.com/w/cpp/language/range-for">range-for</a>)</p></li>
+<li><p>Unrestricted Unions (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2544.pdf">n2544</a>)</p></li>
 </ul>
 <h3 id="excluded-features">Excluded Features</h3>
 <ul>

doc/hotspot-style.md

@@ -1067,6 +1067,9 @@ and other supported compilers may not have anything similar.
 ([n2930](http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2930.html))
 ([range-for](https://en.cppreference.com/w/cpp/language/range-for))
 
+* Unrestricted Unions
+([n2544](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2544.pdf))
+
 ### Excluded Features
 
 * New string and character literals