Progress bar can behave erratically

[13xforever]

Current implementation of ISO9660 reader does not support multi-extent files, so sector ranges and file sizes can report truncated values.

Switching to UDF reader is not an option: it does not implement some features used for PS3 volumes, and does not expose required data, such as sector ranges.

In the short term there needs to be a rework to not rely on the reader structures for progress reporting, in the long term we need better joliet/udf library.