Changes

Discuss: Ctrl-W on last tab should not close firefox. Ref: [https://bugzilla.mozilla.org/show_bug.cgi?id=236721 bug in bugzilla].

Ctrl+w should behave as the tab bar's close button already does, and as Ctrl+F4 already does, and as right click on tab -> "Close tab" already does. Ctrl+w and File->Close Tab should be consistent with every other tab-closing