Merge new changes to unordered & hash.

- Unordered tests can run lightweight test or Boost.Test (at least
   theoretically).
 - Workaround Open BSD's incorrect numeric_limits.
 - Move the hash extensions in their own file.
 - Various small improvements to the unordered docs.
 - Fix some unordered examples.

Merged revisions 43117-43837 via svnmerge from 
https://svn.boost.org/svn/boost/branches/unordered/trunk


[SVN r43838]

doc/src_code/intro.cpp

@@ -0,0 +1,30 @@
+
+// Copyright 2006-2008 Daniel James.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//[intro_example1_1
+#include <boost/unordered_map.hpp>
+#include <boost/foreach.hpp>
+#include <cassert>
+#include <iostream>
+//]
+
+int main() {
+//[intro_example1_2
+    typedef boost::unordered_map<std::string, int> map;
+    map x;
+    x["one"] = 1;
+    x["two"] = 2;
+    x["three"] = 3;
+
+    assert(x.at("one") == 1);
+    assert(x.find("missing") == x.end());
+//]
+
+//[intro_example1_3
+    BOOST_FOREACH(map::value_type i, x) {
+        std::cout<<i.first<<","<<i.second<<"\n";
+    }
+//]
+}