keybindings: Fix style
display: Kill some bad whitespace
keybindings: Handle META_KEY_ABOVE_TAB in get_keycodes_for_keysym

We're going to switch to get_keycodes_for_keysym for the other
bindings, so add that special case here.
keybindings: Rename and move keysym_to_keycode

This makes it more what it's actually doing.