Revert get_users_of_blog() to 3.0 behavior and deprecate. Use get_users() in...

Revert get_users_of_blog() to 3.0 behavior and deprecate. Use get_users() in core. Props scribu. fixes #15854

git-svn-id: https://core.svn.wordpress.org/trunk@17084 1a063a9b-81f0-0310-95a4-ce76da25c4cd