Fix sce_lbn parsing for missing 0x, etc.
Fix basic seeking within an lbn raw file.
Fix it so headless can actually mount isos.
Make filesystem prefix matching case fold.

Even Ms0:/, disC0:/ and HoSt0:/ etc. work.
Return an error if the raw lbn is too high.
Merge pull request #370 from unknownbrackets/lbn

Fix sce_lbn handling