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/key_store.hh
--- src/key_store.hh.orig
+++ src/key_store.hh
@@ -19,8 +19,8 @@
 #include <botan/libstate.h>
 #endif
 
-#include "vector.hh"
 #include "vocab.hh"
+#include "vector.hh"
 #include "paths.hh"
 
 class app_state;