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/file_io.cc
--- src/file_io.cc.orig
+++ src/file_io.cc
@@ -12,9 +12,9 @@
 #include <fstream>
 
 #include <botan/botan.h>
-#include "botan_pipe_cache.hh"
 
 #include "file_io.hh"
+#include "botan_pipe_cache.hh"
 #include "sanity.hh"
 #include "simplestring_xform.hh"
 #include "charset.hh"