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/update.cc
--- src/update.cc.orig
+++ src/update.cc
@@ -9,9 +9,9 @@
 
 #include "base.hh"
 #include <set>
+#include "lexical_cast.hh"
 #include "safe_map.hh"
 #include "vector.hh"
-#include "lexical_cast.hh"
 
 #include "database.hh"
 #include "sanity.hh"