Replace our home-grown BitCast with bit_cast from Chrome/Google3.

src/double.h

Index: src/double.h
diff --git a/src/double.h b/src/double.h
index 7b4486728aaf4094c0a639918290e77ecff0ff6a..cb12628675145db2150e9bf3ba1bf0beb5b65231 100644
--- a/src/double.h
+++ b/src/double.h
@@ -11,8 +11,8 @@ namespace v8 {
 namespace internal {
 
 // We assume that doubles and uint64_t have the same endianness.
-inline uint64_t double_to_uint64(double d) { return BitCast<uint64_t>(d); }
-inline double uint64_to_double(uint64_t d64) { return BitCast<double>(d64); }
+inline uint64_t double_to_uint64(double d) { return bit_cast<uint64_t>(d); }
+inline double uint64_to_double(uint64_t d64) { return bit_cast<double>(d64); }
 
 // Helper functions for doubles.
 class Double {