Don't use "page" variable names for WT_REFs: it's confusing.
Don't skip pages when writing a checkpoint if the transaction doesn't have a checkpoint.  This happens in several paths, including for metadata checkpoints, and also on close.

refs #969, #963, maybe #976?
whitespace
Add a big honkin' comment to explain when checkpoint can safely skip writes.
When restoring a page with updates after a split, free any resources cached in the cursor.

refs #971
The disk header in a page is read-only: mark it const.