ES:BP address of 8x8 font-definition info for > chars 128
Info: This just saves ES:BP into the vector for INT 1fH; that is it
defines how the BIOS will display characters from 80H-ffH when in
CGA-graphics mode (200 vertical res).
ES:BP points to a table containing the character-definition codes. It
should be 2048 bytes long.
Note: This fn requires that you modify BP. When calling from high-
level languages such as C, be very careful to save and restore
BP, since it is used to keep track of the "stack frame".