Blender Git Loki

Windows: use Wintab by default if it's available and a device is detected.

Previously Automatic tablet API mode would handle both Windows Ink and
Wintab events. This is unpredictable and causes problems with the fix
coming in the next commit.

Instead assume that in most cases where Windows Ink is desired there
will be no Wintab. If that's not the case, it can be adjusted under
Preferences > Input > Tablet.