type_url_form_image() becomes wp_media_insert_url_form(), media_upload_image()...

type_url_form_image() becomes wp_media_insert_url_form(), media_upload_image() becomes wp_media_upload_handler(). type_url_form_* and media_upload_* are restored as wrappers. Don't deprecate yet. see #17578.

git-svn-id: https://core.svn.wordpress.org/trunk@18894 1a063a9b-81f0-0310-95a4-ce76da25c4cd