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

Change-Id: I7f71b4a12f99c5f81771146c66629ae5a947b229
diff --git a/src/mem_map.cc b/src/mem_map.cc
index f322773..800f274 100644
--- a/src/mem_map.cc
+++ b/src/mem_map.cc
@@ -16,12 +16,12 @@
 
 #include "mem_map.h"
 
-#include "ScopedFd.h"
-#include "stringprintf.h"
-#include "utils.h"
-
 #include <corkscrew/map_info.h>
 
+#include "base/stringprintf.h"
+#include "ScopedFd.h"
+#include "utils.h"
+
 #define USE_ASHMEM 1
 
 #ifdef USE_ASHMEM