Change the books hash example to have a separate header.

[SVN r28340]

examples/books.hpp

@@ -0,0 +1,26 @@
+
+//  Copyright Daniel James 2005. Use, modification, and distribution are
+//  subject to 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)
+
+// This example illustrates how to use boost::hash with a custom hash function.
+// The implementation is contained in books.cpp
+
+#include <cstddef>
+#include <string>
+
+namespace library
+{
+    struct book
+    {
+        int id;
+        std::string author;
+        std::string title;
+
+        book(int i, std::string const& a, std::string const& t)
+            : id(i), author(a), title(t) {}
+    };
+
+    bool operator==(book const&, book const&);
+    std::size_t hash_value(book const&);
+}