boost: split stream classes out of serialize.h

serialization now has no dependencies.

src/core_write.cpp

@@ -9,6 +9,7 @@
 #include "script/script.h"
 #include "script/standard.h"
 #include "serialize.h"
+#include "streams.h"
 #include "univalue/univalue.h"
 #include "util.h"
 #include "utilmoneystr.h"