Log Message:
Update user-darwin to version 20151015.

Increase the pkgsrc UID range to 300-499.  We can no longer afford to avoid
conflicts with the 400-499 range used by Fink, as pkgsrc now has around 200
users and the previous range was insufficient for bulk builds.

Ideally there would be a way to use a temporary OpenDirectory database for
builds, as while a large range is required for full bulk builds and we're going
to hit even this additional limit soon, it's unlikely a user installation will
require the full range.  However, finding a way to do this is proving elusive.