Fix building d8 with readline support due to API changes

After recent API changes, d8 will fail to build when passing
"console=readline". This patch makes d8 work with readline again.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/125043006

Patch from Adrian Perez de Castro <aperez@igalia.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18457 ce2b1a6d-e550-0410-aec6-3dcde31c8c00