A function macro named E clashes with internal boost definitions.  Rearrange
the order of header inclusion so that affected boost headers are included
before monotone defines the macro.

Also, stop bundling boost/circular_buffer, which is available in current
versions of boost. From Fedora.

Index: src/database.hh
--- src/database.hh.orig
+++ src/database.hh
@@ -11,10 +11,10 @@
 #ifndef __DATABASE_HH__
 #define __DATABASE_HH__
 
-#include "vector.hh"
 #include <set>
 #include <boost/function.hpp>
 #include <boost/shared_ptr.hpp>
+#include "vector.hh"
 
 #include "rev_types.hh"
 #include "cert.hh"