utils: tsig argument: if alg unspecified, using sha256

Closes #514

See merge request !698

Journal evolution

See merge request !697

...because the merged changes had been pushed to insert queue and
inserted after drop_journal!!

Daniel Kahn Gillmor authored 7 years ago and Daniel Salzman committed 7 years ago

At NDSS 2017's DNS privacy workshop, I presented an empirical study of
DNS padding policies:

https://www.internetsociety.org/events/ndss-symposium/ndss-symposium-2017/dns-privacy-workshop-2017-programme#session3

The slide deck is here:
https://dns.cmrg.net/ndss2017-dprive-empirical-DNS-traffic-size.pdf

The resulting recommendation from the research is that a simple
padding policy is relatively cheap and still protective of metadata
when DNS traffic is encrypted:

 * queries should be padded to a multiple of 128 octets
 * responses should be padded to a multiple of 468 octets

Since future research could propose even better policies, and future
DNS traffic characteristics might evolve, I've implemented this
recommendation as a new function in libknot:
knot_edns_default_padding_size()

This changeset also modifies kdig to use this padding policy by
default when doing queries over TLS, and defines +padding (with no
argument) as a kdig option that forces the use of the default padding
policy.

With this changeset, any libknot user who wants to use "a sensible DNS
padding policy" can just rely on the library; this means that if a
better padding policy is determined in the future, it can be
distributed to all users by upgrading libknot.

journal: fixed EINVAL on (zone load + histiory discontinuity + dnssec)

See merge request !696

utils: replace index function for strchr

See merge request !695

stats: fix missing 'zone' keyword in the YAML ouput

See merge request !694

Journal fixes

See merge request !693

added surmised C indentation rules for emacs users

See merge request !691

dynarray: modified to be exportable as symbols; added foreach

See merge request !679

Ddns forward tsig

See merge request !689

Update report time

See merge request !690

kdig: added [no]crypto option omitting binary dump of keys

See merge request !682