int write_string(x,len,shadow,row,col)
char *x;       /* string to be written */
int len;       /* max # of bytes to be written */
char shadow;   /* shadow (attribute) character */
int row,col;   /* row and column of first character */
The write_string function displays the len first bytes of x using the
attribute given by shadow and starting from position (row,col).
There is no return value.
A message for the user on the bottom line of the screen is produced typically by:
write_string(space,c3+8,' ',r3+2,1);           /* Erase bottom line r3+2 */
write_string("Press any key!",14,'1',r3+2,1);  /* Give message in 'red' */