Header update with info about the current status of C++17

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@297022 91177308-0d34-0410-b5e6-96231b3b80d8

www/cxx1z_status.html

@@ -35,7 +35,8 @@
   <h1>libc++ C++1z Status</h1>
   <!--*********************************************************************-->
 
-  <p>In November 2014, the C++ standard committee created a draft for the next version of the C++ standard, known here as "C++1z" (probably to be C++17)</p>
+  <p>In November 2014, the C++ standard committee created a draft for the next version of the C++ standard, known here as "C++1z" (probably to be C++17).</p>
+  <p>In February 2017, the C++ standard committee approved this draft, and sent it to ISO for approval as C++17</p>
   <p>This page shows the status of libc++; the status of clang's support of the language features is <a href="http://clang.llvm.org/cxx_status.html#cxx17">here</a>.</p>
 
   <p>The groups that have contributed papers: