While testing Issue2135 I've become aware how slow the key access is on Windows.

Using a pubring.gpg it takes 1m 56s on my testsystem to try to import the 536
keys from the sks dump before an error occurs. I find this excessive.

I'm saying "try" here because that was a second run where the import was already
done and no key was changed.

With a fresh homedir (keybox) the import only takes ~20sec and a second run ~7sec.

While this is still an order of magnitude slower then on my GNU/Linux system
it's a huge improvement over the keyring.

This makes me wonder if we should migrate the public keyring to keybox for
Windows with 2.1 to fix this issue?
Having only one supported format should also help with maintenance / support.

Werner do you have an opinion on this?