Pass through device class info for touchscreen

So this passes through the EvdevClassTouchscreen from libevdev to
gesture device class as GESTURES_DEVCLASS_TOUCHSCREEN.

BUG=chrome-os-partner:17222
TEST=plugin stantum touch device, make sure there is no error msg
     in /var/log/Xorg.0.log    like
[114197.687] (EE) ERROR:src/gestures.cc:314:Filters are not composed yet!

Change-Id: I349a37939db7890883f99f5f969afd38eaef9725
CQ-DEPEND=Idc4e2f7e
Reviewed-on: https://gerrit.chromium.org/gerrit/41235
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Queue: Yufeng Shen <miletus@chromium.org>
Tested-by: Yufeng Shen <miletus@chromium.org>
1 file changed