Most changes from review comments implemented. Remove use of "#elif" for

backward PP compatability. Add BOOST_category_item_AVAILABLE as a
defined, or not, symbol for use with "#ifdef" or "#ifndef". Add
documentation of macros used for detection and version information. Also
replace direct use of BVN(0,0,0) and BVN(0,0,1) with more meaningful
macros that are globally defined, and hence consistent.

doc/html/index.html

@@ -57,7 +57,7 @@
 </table></div>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: January 11, 2013 at 03:32:51 GMT</small></p></td>
+<td align="left"><p><small>Last revised: January 19, 2013 at 03:18:05 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>

doc/html/predef/reference/boost_arch_architecture_macros.html

@@ -495,30 +495,6 @@
                 </p>
               </td>
 </tr>
-<tr>
-<td>
-                <p>
-                  <code class="computeroutput"><span class="identifier">__x86_64</span></code>
-                </p>
-              </td>
-<td>
-                <p>
-                  <span class="bold"><strong>detection</strong></span>
-                </p>
-              </td>
-</tr>
-<tr>
-<td>
-                <p>
-                  <code class="computeroutput"><span class="identifier">__x86_64__</span></code>
-                </p>
-              </td>
-<td>
-                <p>
-                  <span class="bold"><strong>detection</strong></span>
-                </p>
-              </td>
-</tr>
 </tbody>
 </table></div>
 <h5>