Linux host running on MacBook Hardware: Default release key should be left-winkey

Here's a simple one:

The default key to release a captured mouse from the VBox window is right-ctrl. Quite rightly it is set to Left-Command when running on an OSX host, because some hardware, such as a MacBook Pro, doesn't have such a button, and you'll be unable to free your mouse without some annoyance.

However the same decision isn't taken when you run on Linux (or, I imagine, Windows,) running on a MacBook. It'd be neat if the installer would figure out that we're on an Apple device and set the release key to something different!