Tweaked bootleg cover-art heuristics to use CD-ROM jewel case icon style for earlier games.
Finessed ADBShadowedFilesystem's file-deletion behaviour and made ADBLocalFilesystem's file-open method properly return errors on failure.
Fixed edge-case in drive shadowing where a stat() call could return a stats block for an ostensibly deleted file, causing DOSBox to think that the deletion of that file had failed.