C++11 style guide: Ban alignas/alignof for now.

This patch moves C++11 alignment features (alignas/alignof) to the
banned language features section, since MSVS 2013 does not support them.

MSVS 2015 seems to support them, so we can revisit once MSVS 2015 is
rolled out.

Discussion thread:
https://groups.google.com/a/chromium.org/forum/#!msg/cxx/rwXN02jzzq0/CpUc1ZzMBQAJ

BUG=none

Review URL: https://codereview.chromium.org/1509123002

Cr-Commit-Position: refs/heads/master@{#363798}

Author: yutak

styleguide/c++/c++11.html

@@ -425,6 +425,25 @@ <h3 id="blacklist_banned"><a name="core-blacklist"></a>C++11 Banned Features</h3
 <th style='width:240px;'>Notes</th>
 </tr>
 
+<tr>
+<td>Alignment Features</td>
+<td>
+<code>alignas</code> specifier,
+<code>alignof</code> operator
+<td>Object alignment</td>
+<td>
+<a href="http://en.cppreference.com/w/cpp/language/alignas">alignas</a>,
+<a href="http://en.cppreference.com/w/cpp/language/alignof">alignof</a>
+</td>
+<td>
+<a href="https://codereview.chromium.org/1497963002/">Doesn't work in
+MSVS2013</a>.
+<a href="https://msdn.microsoft.com/en-us/library/dn956970.aspx">MSVS2015
+supports them</a>; reevaluate after MSVS2015 is available.
+<a href="https://groups.google.com/a/chromium.org/d/msg/cxx/rwXN02jzzq0/CpUc1ZzMBQAJ">Discussion thread</a>
+</td>
+</tr>
+
 <tr>
 <td>Constant Expressions</td>
 <td><code>constexpr</code></td>
@@ -584,16 +603,6 @@ <h3 id="blacklist_review"><a name="core-review"></a>C++11 Features To Be Discuss
 <th style='width:240px;'>Notes</th>
 </tr>
 
-<tr>
-<td>Alignment Features</td>
-<td>
-<code>alignas</code> specifier,
-<code>alignof</code> operator,
-<td>Object alignment</td>
-<td><a href="http://en.cppreference.com/w/cpp/language/alignof">alignof</a></td>
-<td></td>
-</tr>
-
 <tr>
 <td>Attributes</td>
 <td><code>[[<i>attribute_name</i>]]</code></td>