seat: don't add POINTER capability to tablets
Having WL_SEAT_CAPABILITY_POINTER
as soon as a tablet is present, even
if it isn't used, causes several issues:
- primary problem: a pointer is displayed on screen with no way to get rid of it
- annoying side effect: docked mode in Phosh is always enabled (this deserves a fix of its own, but in the current state it's still a major problem)
Getting rid of the POINTER capability for tablets solves both those issues, without impacting usability: Phoc is already able to detect when the stylus is "close enough" (based on TABLET_TOOL_PROXIMITY events), and displays the pointer only in that case (which is how it should be handled, IMHO).
Tested on MS Surface Pro 3 w/ Surface Pen, would welcome additional testing with a Wacom USB tablet.
Fixes #215 (closed)