BLOCKED add defcfg "linux-use-trackpoint-property" to set the pointingstick property on kanata's virtual device

[wolfwood]

Describe your changes. Use imperative present tense.

add defcfg "linux-use-trackpoint-property" to set the pointingstick property on kanata's virtual device. resolves #586

Checklist

• Add documentation to docs/config.adoc
  • [x] Yes or N/A
• Add example and basic docs to cfg_samples/kanata.kbd
  • [x] Yes or N/A
• Update error messages
  • [x] Yes or N/A
• Added tests, or did manual testing
  • [x] Yes

I wanted to get some feedback on this approach before completing the checklist.

This is blocked by the bug in evdev-0.12.1, since this patch depends on a method introduced in that version. see emberian/evdev#129

I was initially hoping to dynamically detect trackpoints in KbdIn and then alter the virtual device created by KbdOut accordingly. However, the KbdOut is created first so the dynamic approach would require rearchitecting a bit.

Instead I opted for a config option. It should be noted that if you change the new setting, linux-trackpoint, live reloading is not sufficient for the change to take effect. It might be possible to fix this and if so the dynamic approach might be easier than I thought.

[jtroo]

linux-trackpoint, live reloading is not sufficient for the change to take effect

This limitation is fine; other device-related settings also don't live-reload properly.

[jtroo]

As the PR title you chose states, the code will not be merged in so long as the path name issue exists in evdev, but generally seems like a fine code change.

[wolfwood]

I've tested to confirm the path name issue is resolved with evdev-0.12.2.