Clipboard fixes (for 6.1?) Hi, Here is a few fixes I have collected while working on clipboard-related code. There are some obvious code improvements/fixes, and better handling of release & unregister to avoid dangling pointers and improve user experience. v3: - add a migration blocker - improve the code by using a few helpers v2: - replaced "ui/vdagent: unregister clipboard peer on finalize" with "ui/vdagent: disconnect handlers and reset state on finalize" patch. - added "ui/vdagent: reset outbuf on disconnect" - commit message tweaks