Add X event buffering for cloaking user input patterns

[Aaron Rainbolt]

Heya! I just made a draft PR for qubes-gui-daemon that implements input event buffering and obfuscation. This is supposed to help the user remain anonymous even on websites that attempt to track input device patterns, and may be especially useful in Whonix.

The PR is here: https://github.com/QubesOS/qubes-gui-daemon/pull/149 It's a draft still, I'm hoping to get some feedback on it before spending too much additional time on it (just in case the existing implementation isn't considered a good idea). Rationale for the implementation method is included, along with next steps to get the PR in a merge-worthy state.

Thanks for your time! Hope this is helpful.

Aaron