Without --xdf, DiskDump simply dumps an XDF disk image as a vanilla 80-track, 23-sectors-per-track disk image.
In addition, I regenerated all the PC-DOS 7.00 disk images without --xdf, to see if that works any better (it seems to work for VirtualBox)
Some other interesting bugs were fixed along the way:
the Video component incorrectly assumed that masking a negative number with 0x80000000 would yield 0x80000000 (it actually yields -0x80000000, thank you JavaScript);
the ChipSet component provides a new addCMOSMemory() interface that RAM objects can use to bump the CMOS total to match the actual total;
the CPU properly implements INSW and OUTSW instructions now (kind of important for the AT hard disk controller)
