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>

private.h

@@ -36,6 +36,7 @@ int       client           (int argc, char *argv[]);
 void      service_bootstrap(void);
 void      service_monitor  (pid_t lost);
 
+void      plugin_run_hook  (hook_point_t no, void *arg);
 void      plugin_run_hooks (hook_point_t no);
 int       plugin_load_all  (uev_ctx_t *ctx, char *path);