Use ldexp instead of pow for more accuracy.
Use ldexp instead of pow for more accuracy.

Original patch by net147@gmail.com: https://chromiumcodereview.appspot.com/10026011/

BUG=
TEST=cctest/test-conversions/Octal

Review URL: https://chromiumcodereview.appspot.com/10103030

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@11356 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh