If a checkpoint operation fails on a tree, make sure it ends up marked dirty.  When discarding a tree, if there are updates that are too recent to discard, fail with EBUSY rather than asserting.
Merge pull request #1299 from wiredtiger/tree-modified

If a checkpoint operation fails on a tree, make sure it ends up marked dirty
If the metadata is updated, that update should ignore the running transaction.  In particular, it should not be rolled back if WT_SESSION::rollback_transaction is called.
Use the whole buffer for config strings: we just calculated the length we need.
Fix line wrapping.
All log operations need the file ID, set it when allocating the structure.