This is the first part of removing calls to gay's strtod. Future CLs will
get rid of calls to gay_strtod entirely.

BUG=
TEST=

Review URL: http://codereview.chromium.org/3563009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5600 ce2b1a6d-e550-0410-aec6-3dcde31c8c00