Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/include/v8-version.h b/include/v8-version.h
index c1231d4..f155b8a 100644
--- a/include/v8-version.h
+++ b/include/v8-version.h
@@ -8,10 +8,10 @@
 // These macros define the version number for the current version.
 // NOTE these macros are used by some of the tool scripts and the build
 // system so their names cannot be changed without changing the scripts.
-#define V8_MAJOR_VERSION 4
-#define V8_MINOR_VERSION 9
-#define V8_BUILD_NUMBER 385
-#define V8_PATCH_LEVEL 28
+#define V8_MAJOR_VERSION 5
+#define V8_MINOR_VERSION 0
+#define V8_BUILD_NUMBER 71
+#define V8_PATCH_LEVEL 48
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)