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/src/conversions.h b/src/conversions.h
index 9b6d83b..29262e5 100644
--- a/src/conversions.h
+++ b/src/conversions.h
@@ -172,7 +172,7 @@
 // Convert from Number object to C integer.
 inline int32_t NumberToInt32(Object* number);
 inline uint32_t NumberToUint32(Object* number);
-
+inline int64_t NumberToInt64(Object* number);
 
 double StringToDouble(UnicodeCache* unicode_cache, Handle<String> string,
                       int flags, double empty_string_val = 0.0);