Add DNS support, comprising...

WIP on DNS.

Start of test harness.

Return leaf hash.

Temporarily include Eran's https://codereview.appspot.com/66940043/.

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.

Fix merge error.

Add ldns library to LOCAL_LIBS.

Missing space.

Log instead of stderr.

Missing black line.

Remove redundant forward declarations.

Fix incorrect indent.

Run the DNS tests as part of the test suite.

Closes #25.

Remove redundant .. include.