Do not update the whole screen in -m mode

[cheater]

When in -m, do not update the whole screen. Have the cursor move around the screen and only rewrite the parts that are necessary to update. This is, for example, how "watch" does this, as well as all the others (top, irssi, ...). Updating the whole screen makes it impossible to copy stuff out of the terminal, which is super annoying.

You can likely do this by using the right lib for terminal display or the right options to it.