Add absolute coordinates for tablets. Absolute coordinates is relative to window so it can't work for multiple displays? Doesn't work for single display without mouse driver modification.
Add arbitrary number of buttons. Previously, only one mouse button was supported.
Add arbitrary number of bits. Previously, only 7 bits per axis was supported which is good enough for relative movement but not absolute movement.
Result of running IWYU (https://include-what-you-use.org/) and
applying most of the suggestions about unncessary includes and
forward declarations.
Was motivated by observing that <thread> was being included in
ppcopcodes.cpp even though it was unused (found while researching
the use of threads), but seems generally good to help with build
times and correctness.
