[RFC v2] xserver: Masked valuators, mixed modes, DIDs, and ABS_MT_SLOT

[Henrik Rydberg]

Hi Chase,
> * Many fixes found through further review
> * Redo rangeToMask translation for ranged event APIs
>   - No longer allocates memory except a bitmask (6 bytes) on the stack

Calling set_raw_valuators() with a subranged valuators array will cause a
segfault, which could be fixed by using the construction found in set_valuators().

Thanks,
Henrik