Try preventing static casts when calling hash_value.

[SVN r63716]

test/shared_ptr_fail_test.cpp

@@ -0,0 +1,11 @@
+#include <boost/functional/hash.hpp>
+#include <boost/shared_ptr.hpp>
+
+// This should obviously pass if shared_ptr ever supports Boost.Hash.
+
+int main() {
+    boost::hash<boost::shared_ptr<int> > hash;
+    boost::shared_ptr<int> x(new int(10));
+    
+    hash(x);
+}