1. Switch to low-level console routines for performance improvements.
2. Instead of moving the cursor around like a real tty, just track the
destination coordinates of where the cursor should be, and
defer the movement until user input is expected.
Credit to <Someone> for #2.
From a bug report. I can't test this fix, but
inspection of the code shows that his suggested fix is clearly
necessary. Once `bp' gets incremented, storing via `bp[BUFSZ-1]'
writes beyond the bounds of `buf' and clobbers something.
