screen: Update for vte API

Corresponding to vte commit a14008988f755d7d5241bc9086173ebdcdad0b8f.
screen: Update for vte API

Corresponding to vte commit 68011996d3910389f1b5cfb0a7e47a20ea67004f.
screen: Update for vte API

Corresponding to vte commit 165b0cf9c40cddf6235e42d86a434b9a1cffaea5.