Prevent two enforce tasks to run concurently. This could happen when manually issueing an enforce.

Conflicts:
	enforcer-ng/src/daemon/engine.c
	enforcer-ng/src/enforcer/enforce_cmd.cpp
	enforcer-ng/src/enforcer/enforce_task.cpp

Conflicts:
	enforcer-ng/src/daemon/engine.c
	enforcer-ng/src/enforcer/enforce_cmd.cpp
	enforcer-ng/src/enforcer/enforce_task.cpp
Never call a key dead. In 1.x a dead key was never displayed. Call it retired.
If DS is seen but not all TTLs passed (ds would be rumoured) call it active instead of ready.
Check the pidfile to prevent 2 instances running at once.

Conflicts:
	enforcer-ng/src/daemon/engine.c

Conflicts:
	enforcer-ng/src/daemon/engine.c
lost a "}" in the cherry pick
Do not pass negative value to kill. It will try to signal itself/processgroup
Merge pull request #52 from yschaeff/bb

Backport a couple of fixes from client_stderr branch