Update the generators implementation to make "next" also do the job of
what was previously called "send" by taking an optional argument.
Remove send, and do a bunch of renamings.

R=rossberg@chromium.org
BUG=v8:2355, v8:2715

Review URL: https://codereview.chromium.org/16136011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15028 ce2b1a6d-e550-0410-aec6-3dcde31c8c00