Use built-in linking rules (with its own variables).
Merge remote-tracking branches 'origin/cleanup/whitespace-1', 'origin/build-implicit-link' and 'origin/build-jsonc' into integrate

Conflicts:
	cpp/Makefile
WIP on DNS.
Start of test harness.
Return leaf hash.
Also verify an inclusion proof for a leaf's hash.
Test work in progress.
Add missing file, move unmoved file.
Allow binary SCTs and logs on protocols other than HTTPS.
Remaining issues after a rebase.
Fix a couple of stray "https:"s.
Log responses.
Correct path.
Show error content.
Identify the type of the cert in the file name.
Calculate the right audit path length.
Get rid of cruft.