vte >= 0.37 expores API version 2.91, which is where all the active
development is. qemu builds and runs fine with that version, so use it
if it's available.

Signed-off-by: Cole Robinson <crobinso@redhat.com>
Message-id: b4f0375647f7b368d3dbd3834aee58cb0253566a.1462557436.git.crobinso@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>