diverging from upstream defaults

[Vincent Breitmoser]

Picking up on the s2k default:

>> I am not sure about the 100ms vs. 300ms change for S2K.
> I hope someone will speak up if they have that use case.

I don't have "that" use case, but it's probably worth mentioning that
moving a 100ms-adjusted key from a desktop machine to a smartphone can
already be problematic even with 100ms. Particularly if the desktop
machine is relatively newer than the phone, the difference in speed can
become a factor 10 or more.

Not making a statement about whether to go for 100ms or 300ms here, it's
just a loosely related point that has caused us a few confused users in
the past and might be non obvious to people who don't use OpenPGP on a
phone.

 - V