[PATCH RFC] Support for new XInput ABI in synaptics

[Ben Gamari]

I got sick of not having a working trackpad with todays xserver build so I took
a few minutes to fix up the synaptics driver to be compatible with the new
XInput ABI. The task was generally pretty simple although it's definitely not
finished.

The synaptics driver claims it can export up to 12 buttons but there is no
indication of what these buttons might be. I inferred the first few (probably
incorrectly), but I have no idea what the rest might be. If someone wants to
either finish the patch themselves (filling in the region near the TODO) or let
me know what these buttons might do, synaptics will work once again with
xserver master.

Thanks,

- Ben