Fix memory leaks in test/checkpoint. As reported by Coverity.
Fix build warning.
Clean up error handling in test/checkpoint.
Allow "wt salvage" of any URI.
Copy log files before data files in hot backups.  This addresses a problem where recovery rolls the metadata forward past the most recent checkpoint in a data file, so that it can no longer be opened.

refs #976
Make sure changes performed by the checkpoint transaction are logged.

refs #972, #979
Change to always copying log files during hot backup, regardless of whether a target was specified.  Recovery can cope with missing files.  Fixes a warning:

src/cursor/cur_backup.c:205:5: error: 'target_list' may be used uninitialized in this function
Go back to only copying log files when doing a full backup, but still copy logs before data files.

refs #976