Draft content gets filtered, possibly munging data [w/ patch]

[coffee2code]

Drafts are not always completed posts (perhaps having been saved in mid-writing to avoid losing the post in an unexpected browser crash). Since both the excerpt and content text get filtered, this could lead to problems, such as the balanceTags filter tacking close tags to the end of the incomplete post. Who knows what other filters/plugins would do to partial posts saved as drafts.