Move stringpiece.h and stringprintf.h to base/.

Change-Id: I7f71b4a12f99c5f81771146c66629ae5a947b229
diff --git a/src/dex2oat.cc b/src/dex2oat.cc
index 70b2a6b..e434c29 100644
--- a/src/dex2oat.cc
+++ b/src/dex2oat.cc
@@ -24,6 +24,7 @@
 #include <vector>
 
 #include "base/stl_util.h"
+#include "base/stringpiece.h"
 #include "base/unix_file/fd_file.h"
 #include "class_linker.h"
 #include "class_loader.h"
@@ -37,7 +38,6 @@
 #include "ScopedLocalRef.h"
 #include "scoped_thread_state_change.h"
 #include "sirt_ref.h"
-#include "stringpiece.h"
 #include "timing_logger.h"
 #include "well_known_classes.h"
 #include "zip_archive.h"