make the various combinations of arrow keys and shift/control/meta work

make the various combinations of arrow keys and shift/control/meta work

When using st with screen, I've bound next, prev, new screen to
combinations like Ctrl-Alt-Right,Left,Down; xterm and (u)rxvt work fine
when this combination of modifiers is pressed, st does not seem to
transport all of them; a single modifier key is fine (e.g. Ctrl-Up,
Alt-Down etc., but combinations are not). While I'm not terribly
familiar with this, I have tried to hack config.h in a more or less
systematic way to generate the expected sequences.