libchromeos: split dbus_utils.h/extract data serialization routines

Split chromeos/dbus_utils.h into chromeos/dbus/utils.h and
chromeos/dbus/data_serialization.h to separate general D-Bus
utilitiles (such as error handling) from D-Bus-to-native-C++ data
marshaling code.

Updated dependent code with the changed include file names.

BUG=None
TEST=FEATURE=test emerge-link libchromeos buffet peerd

Change-Id: I54ad22c0eb0483df479c23652413c80c384b6be3
Reviewed-on: https://chromium-review.googlesource.com/214461
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/buffet_client.cc b/buffet/buffet_client.cc
index c42e484..38ea239 100644
--- a/buffet/buffet_client.cc
+++ b/buffet/buffet_client.cc
@@ -14,7 +14,7 @@
 #include <base/values.h>
 #include <chromeos/any.h>
 #include <chromeos/data_encoding.h>
-#include <chromeos/dbus_utils.h>
+#include <chromeos/dbus/data_serialization.h>
 #include <dbus/bus.h>
 #include <dbus/message.h>
 #include <dbus/object_proxy.h>