Tony Finch authored Jan 31, 2019 and Evan Hunt committed May 08, 2019

This makes the `-12a` options to `dnssec-dsfromkey` work more like
`dnssec-cds`, in that you can specify more than one digest and you
will get multiple records. (Previously you could only get one
non-default digest type at a time.)

The default is now `-2`. You can get the old behaviour with `-12`.

Tests and tools that use `dnssec-dsfromkey` have been updated to use
`-12` where necessary.

This is for conformance with the DS/CDS algorithm requirements in
https://tools.ietf.org/html/draft-ietf-dnsop-algorithm-update