remove copypasta from vga library. The modex16 routines are a better fit

for the code at this time. I have a few questions about #defines. Add
reminder to self (or Sparky4) that the modex16 library could benefit
from an enum or #define constants to make the code more readable where
calls to modex16 are involved setting up VGA X modes (i.e what does "0"
and "1" mean in the first param?).