changes for qt5 on mac

- setShown() -> setVisible()
- qt_mac_set_menubar_icons() no longer exported, use alternative method
more qt5 mac fixes

- workaround for -psn_0 being passed in
- use fusion if plastique missing
failure to find a field should not break entire query

https://anki.tenderapp.com/discussions/ankidesktop/656-unexpected-results-on-search-with-boolean-or-operator