Use "$(MAKE) -C ..." for running make in subdirectories.

This adds announcements on changes of directory, helping see what happens
better.
Merge branch 'master' into integrate

Conflicts:
	Makefile
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.
Get rid of trailing whitespace.
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.