added Arch Linux
Update settings-schema.json
Fix checkbox allocation
windownManager.js: compositor "destroy" events will be received for non-visible,
but attached windows now (modal popups attached to the titlebar of their parent) -
allow them, but don't perform any effects.  This is just to allow the parent un-dimming
to occur correctly.

Fixes #3249
Merge pull request #3299 from penghuanmail/master

Update settings-schema.json
Merge pull request #3310 from collinss/checkbox

Fix checkbox allocation
Merge pull request #3253 from glls/master

added Arch Linux