General code cleanup/refactoring. Added header comments.
Added "use image size" parameter for MSCP disks -- block count derived from image file size rather than DEC drive geometry; allows for arbitrarily large disks (up to 2TB, theoretically.)
without help from the device code (just call request_DMA and when it returns the DMA transfer is complete.) Fixed
request_DMA to chunk DMA transfers larger than 1024 bytes to avoid overrunning the mailbox's shared memory. Fixed
concurrency issues with DMA requests -- a race condition could cause DMA request data to get clobbered.
RT-11 now boots, MSCP behavior is now very reliable.
