i3: Update to version 4.3.

Though upstream clearly recommends to not deactivate Pango, we currently can't
use Pango right now, as we are stuck at cairo-1.10.2. This version only has
experimental support for XCB which became stable in 1.12.x.

So we need to wait for 21bf5ef5

 to be merged
into master before we can enable Pango.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>