Fix #18: Add support for calling run/tasks on HOOK points

This patch implements support for calling run/task jobs on the built-in
`HOOK_*` points in Finit.  To map each HOOK point to a condition a new
classification was made, as shown in plugin.h and in the example below.

task <hook/mount/root> /sbin/attachubi.sh      # run in parallel with other tasks/services
run  <hook/net/up>     /sbin/dosomething.sh    # run in sequence with other commands

Please note, only rudimentary tested.

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

src/private.h

@@ -40,6 +40,7 @@ int       client           (int argc, char *argv[]);
 
 void      service_monitor  (pid_t lost);
 
+const char *plugin_hook_str(hook_point_t no);
 int       plugin_exists    (hook_point_t no);
 void      plugin_run_hook  (hook_point_t no, void *arg);
 void      plugin_run_hooks (hook_point_t no);