wayland: Add wayland client
This patch adds a new client which supports the Wayland input method
protocol. Note that the support is disabled by default until the
input method protocol becomes official in the Wayland upstream.
Supply --enable-wayland to configure to try it. Also, you will need
to set the executable path of ibus-wayland under the "input-method"
section of weston.ini, like this:
[input-method]
path=.../libexec/ibus-wayland
BUG=Issue#1617
Review URL: https://codereview.appspot.com/
11320043
Patch from Jan Arne Petersen <jan.petersen@kdab.com>.