KiCad - the KiCad Bridge

1.0.38: 1.0.38: a KiCad window that was busy loading when the bridge tried to send it behind the user's window is now retried until the push lands. The once-per-window slot was claimed before the push, so a refused push (the editor not answering, usual on a slow machine) used the slot up and KiCad stayed in front for good: kicad_open_board left the PCB Editor on top of the user's window on a 2-core VM, twice. A refusal draws no frame, so the retry cannot strobe. Found by the full verb battery on a from-scratch VM, which otherwise passed 117 of 118 verbs on 1.0.37. The wider problem, that every KiCad window takes the foreground for a few milliseconds before it is bounced, is wiki #112 and is not changed here.