* Add start/end markers to the regex patterns in audio and video embed handlers.
* Move the handler functions registration to wp_maybe_load_embeds().
* Rename both functions to match the wp_embed_handler_* pattern.
* Move the functions closer to wp_embed_handler_googlevideo().

props kovshenin. fixes #24092.

git-svn-id: https://core.svn.wordpress.org/trunk@24000 1a063a9b-81f0-0310-95a4-ce76da25c4cd