[dev] [dvtm] buffered text on resize

When resizing a window in dvtm, the text buffers for each row are resized to
reflect the number of columns. When making a window smaller, this has the
effect of deleting all the text that has gone off the edge of the window.
 If you then make the window larger, that text won't be redrawn - it has
been lost.

I've attached a patch for dvtm that changes the way it handles resizes. Now
it will only resize the buffers if the window is resized so it is larger
than the previous largest. This way the text in the buffers never gets
lost. It has the unfortunate side effect of forcing a redraw on each row
everytime you resize (unless the number of columns doesn't change) but I
think it's worth it. It also reduces the number of memory
allocations/reallocations.

-Niki Yoshiuchi