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

Change-Id: I7f71b4a12f99c5f81771146c66629ae5a947b229
diff --git a/src/base/logging_android.cc b/src/base/logging_android.cc
index 0acf5f9..9b1ac58 100644
--- a/src/base/logging_android.cc
+++ b/src/base/logging_android.cc
@@ -15,11 +15,12 @@
  */
 
 #include "logging.h"
-#include "stringprintf.h"
 
-#include <iostream>
 #include <unistd.h>
 
+#include <iostream>
+
+#include "base/stringprintf.h"
 #include "cutils/log.h"
 
 namespace art {