The non-mac icon was an old version with white foreground and a
completely transparent background, but this looks bad (or invisible)
depending on where you view it. This updates it based on the macos
icon, but with a round white circle background instead of the macos
"squircle" background.
This also replaces the .ico file for the installer with one that we
build during the win32 build rather than a pregenerated one.
Bumps the gui as well to a version with the new icons in place.
