fsck: bug fixes for big endian fsck on small endian box

Also change misc because a signed 16bit value swizzled gets 32bit extended
which tripped the sanity checker wrongly
mtx: Further work on the floppy driver

We now load the superblocks and find the inode etc for init

Note that the order on the virtual disk is odd with the second head after
the first full set of tracks
mtx: Set the crtc up properly
mtx: 80 column driver

Use the crtc to do hardware scrolling
mtx512: Add tools for converting fuzix fs images into mfloppy disk format
mtx512: undo that

Amazing what a floppy bug can look like

The disk order is just fine
mtx: mask sector count on side1

The MTX512 doesn't write sector labels 17-32 on the second side but recycles
1-16