T2G - A program to convert a text screen into a graphics screen

I originally wrote this as part of a program to do a pixelated fade of a text
screen.  This is where instead of the colors slowly fading to black, the
individual pixels turn to black until nothing is left.  This required that
the text be drawn in a graphics mode.  I never did finish the fading program.

The operation of this program is simple.  It reads the text from the screen
and stores it into an array.  Then it sets up graphics mode, and draws each
character from the original text screen using the ROM BIOS character tables.

Since the VGA uses 16 lines per character, at 25 text screen rows this makes
for 400 graphics lines.  There is no standard VGA 400 line mode, so for
simplicity's sake I use the EGA 350 line mode and draw the characters in
the 14 line EGA font.  This means that the graphical screen won't look the
same as the text screen.  I could have set up the VGA 640x480 mode, and then
tweaked the VGA registers to switch it to 400 line mode, but I didn't feel
like it for the extra 2 lines per character it would have given me.
