fix typos in the documentation

doc/tutorial/incomplete-support-for.html

@@ -113,7 +113,7 @@ arguments), which comes down to the follwing two criteria:</p>
 placeholders do contain these).</li>
 </ol>
 <p>If these two hold, you can safely put <tt class="literal"><span class="pre">BOOST_MPL_AUX_LAMBDA_SUPPORT</span></tt> inside
-your metafunction and forget about the issue.  If not, your are out of luck and
+your metafunction and forget about the issue.  If not, you are out of luck and
 probably have to write a metafunction class instead.</p>
 <p>The good news are that most of the MPL's own metafunctions and <a class="reference" href="../../../type_traits/index.html" target="_top">Boost.Type Traits</a>
 templates are &quot;placeholder-safe&quot; and have the workaround applied to them, so