Put your videomode files in this directory.
That is: boot your machine in all videomodes that you are interested in,
and run "restoretextmode -w CxR" where R is the number of rows and C the
number of columns. This yields files 80x25, 132x44, ...

Once you have these, the utility resize will change your videomode.
(See also resize.c. Next time I'll provide a man page.)