current attribute, but has all non-color flags turned off. Use this when
doing erasure, as this allows us to optimize repainting in curses.
XXX The way the default attribute is handled is totally bogus and needs to
be fixed.
min() et al. did unsigned comparisions before)
make ROWS_ABOVE / ROWS_BELOW return signed values, the negative results
occur if the cursor is outside the scrolling region
-display DEC special graphics and DEC technical characters as far as
possible
-implement the font switching controls (need documentation!)
-behave well if double-width characters are requested
-simplify the state machine: store CSI command modifiers in variables
instead of dedicating own states to each of them
It should be able to parse escape sequences up to VT300, but not everything
is implemented. Most notably, there is no font handling - all displayable
characters are handed to the graphics driver. To solve this, a serious
interface change to the graphics driver is needed (Unicode?).
