Add HOOK_SVC_LOST to detect lost processes

This patch adds support for the runtime `HOOK_SVC_LOST` and the (very
noisy) *example* plugin `lost.so`.

Customer request.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugin.h

@@ -51,6 +51,7 @@ typedef enum {
 
 	/* Runtime hooks */
 	HOOK_SVC_RECONF,
+	HOOK_SVC_LOST,
 	HOOK_RUNLEVEL_CHANGE,
 
 	/* Shutdown hooks */