Fix for Redump/XGD ISOs and ISOs with empty directories

[rapperskull]

First commit:

• Add support for XGD1/Redump ISOs
• Use correct offset when rewriting from XDG ISO (now it's possible to directly convert Redump ISOs to XISOs, unlike Skip video partition on redump-style images #46 and my previous attempt Add support for XGD1/Redump ISOs (as input) #45)
• Partially implement Support -o[ffset] option to skip video partition or other headers #33 (I don't think an '-o' option should be needed anymore)

Second commit:

• Don't fail on empty directories (Burnout (Out of memory error with isos that have invalid TOC entries #25), Project Gotham Racing)
• Write directory size as a multiple of sector size, as seen on retail ISOs (please note that this is in contrast to the online sources on the matter)
• Empty directories now use one sector instead of zero, as seen on retail ISOs
• Print empty directories in list mode

[mnadareski]

I just want to chime in that this particular PR worked for a couple of corner-case discs that I have been having an issue with previously, including the aforementioned PGR. ❤️

[MasonT8198]

I have tested this PR, no issues that I can detect other than a known issue with extract-xiso where it can create bad isos as brought to my attention by Vaporeon

edit: I would’ve waited on trying to implement PR #33 in case there may have been a change needed, however I doubt there would’ve been

[MasonT8198]

PR #44 should be a suitable fix to the bad iso issue upon further research, will have to test to confirm the fix

[LukeUsher]

Looks good, thanks!

extract-xiso is basically on life-support at this point and in desperate need of a replacement, however, as it is one of the only open-source cross-platform solutions, this does need to be fixed.