PNaCl documentation: add SIMD vectors.

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 <section id="nacl-and-pnacl">
 <span id="id1"></span><h1 id="nacl-and-pnacl"><span id="id1"></span>NaCl and PNaCl</h1>
 <p>This document describes the differences between <strong>Native Client</strong> and
 <strong>Portable Native Client</strong>, and provides recommendations for when to use each.</p>
 <div class="contents local" id="contents" style="display: none">
 <ul class="small-gap">
 <li><a class="reference internal" href="#native-client-nacl" id="id3">Native Client (NaCl)</a></li>
 <li><a class="reference internal" href="#portable-native-client-pnacl" id="id4">Portable Native Client (PNaCl)</a></li>
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 you can still use the PNaCl toolchain and distribute your application
 through the Chrome Web Store, and thereby take advantage of the
 conveniences of PNaCl, such as not having to explicitly compile your application
 for all supported architectures.</p>
 </section><section id="when-to-use-nacl">
 <span id="id2"></span><h2 id="when-to-use-nacl"><span id="id2"></span>When to use NaCl</h2>
 <p>The limitations below apply to the current release of PNaCl. If any of
 these limitations are critical for your application, you should use
 non-portable NaCl:</p>
 <ul class="small-gap">
-<li>By its nature, PNaCl does not support architecture-specific instructions in
-an application (i.e., inline assembly). Future editions of PNaCl will
-attempt to mitigate this problem by introducing portable intrinsics for vector
-operations.</li>
+<li>By its nature, PNaCl does not support architecture-specific
+instructions in an application (i.e., inline assembly), but tries to
+offer high-performance portable equivalents.</li>
 <li>Currently PNaCl only supports static linking with the <code>newlib</code>
 C standard library (the Native Client SDK provides a PNaCl port of
 <code>newlib</code>). Dynamic linking and <code>glibc</code> are not yet supported.
 Work is under way to enable dynamic linking in future versions of PNaCl.</li>
-<li>In the initial release, PNaCl does not support vector types and SIMD.</li>
 <li>In the initial release, PNaCl does not support some GNU extensions
 like taking the address of a label for computed <code>goto</code>, or nested
 functions.</li>
 </ul>
 </section></section>
 
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