Cleanup Code::Kind2String().

Use CODE_KIND_LIST() to automatically generate the case statements for
Code::Kind2String().

BUG=
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/17571016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15314 ce2b1a6d-e550-0410-aec6-3dcde31c8c00