Remove X11 deps from //ui/events:events_base.

Split out X11 keycode related code from //ui/events:events_base. Add new
targets for XKB and X keycode manipulation.i

Update GYP in similar fashion to GN. Also fix GN check problems that
crop up because GN check doesn't fully understand #if defined(USE_X11)
and includes.

BUG=588026
TBR=watk@chromium.org

Review URL: https://codereview.chromium.org/1880313004

Cr-Commit-Position: refs/heads/master@{#388894}
25 files changed