Implement fast case for strtod.

src/strtod.h

Index: src/strtod.h
diff --git a/src/strtod.h b/src/strtod.h
index c53351f6639d675f99c098d77ca270c268ca6e16..4d256baf2ee343c01236eff6b5a9c11293a6550b 100644
--- a/src/strtod.h
+++ b/src/strtod.h
@@ -33,7 +33,7 @@ namespace internal {
 
 // The buffer must only contain digits in the range [0-9]. It must not
 // contain a dot or a sign. It must not start with '0', and must not be empty.
-double strtod(Vector<char> buffer, int exponent);
+double Strtod(Vector<char> buffer, int exponent);
 
 } }  // namespace v8::internal