Merge riastradh-drm2 to HEAD.

Use Mt for email addresses.

branches: 1.1.6; 1.1.14; 1.1.18;
Update hkpd to return its information in JSON (via libmj).

Add a C HKP client.

Provide reachover Makefiles for each, but do not hook them up to the build
just yet.

The HKP client and server can be embedded in other programs.

sync with HEAD

Rebase to HEAD as of a few days ago.

sync with head.

for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.

this commit was splitted into small chunks to avoid
a limitation of cvs. ("Protocol error: too many arguments")