winex11.drv[2/6]: wintab: skip non-pressure-sensitive devices for wintab32

[Mikolaj Zalewski]

Another problem I had was that the laptop touchpad was detected as a
tablet. This may confuse Windows applications, as on Windows it isn't.
Also it confuses Wine because we support only one tablet - we assume
that each cursors have the same resolution.

Is there a good way to select the correct devices as do we have to add
heuristics like the one in this patch? This patch ignored devices that
don't have the pressure axis. I assume that the WM_MOUSEDOWN gives
enough information so there is little loss that it can't be accessed
with wintab32.