Wait for LRU eviction to complete in the checkpoint thread, without waiting for the eviction server.
We don't need to disable eviction of dirty pages now that we're disabling all eviction in the subtree being checkpointed.
Remove disabled code and rename "writes_disabled" now that all eviction is disabled in the subtree of an internal node being checkpointed.
Fix a comment, compaction no longer goes through the evict-file call.
Use the standard panic calls if we get a sync operation we don't expect.
No real changes.
Back out a change: don't queue dirty pages for eviction during a checkpoint.  It's very unlikely that we'll find a dirty page that we can evict (it would have to be an internal node with no children, ahead of the checkpoint).
Merge pull request #423 from wiredtiger/dirty-disable-mjc

Tweaks to the dirty-disable branch based on review.