[multipathd] DM configuration ground work #2

[multipathd] DM configuration ground work #2

This patch enables DM configuration at multipathd startup.

To achieve that simple goal, the following steps were necessary :

- new libmultipath/structs_vec.[ch] exporting high level method working
  on [vectored] {path,multipath} structs :
	- set_no_path_retry
	- adopt_paths
	- orphan_paths
	- orphan_path
	- verify_paths
	- update_mpp_paths
	- setup_multipath
	- update_multipath_strings
	- remove_map
	- stop_waiter_thread_func *stop_waiter, int purge_vec);
	- remove_maps
	- add_map_without_path
	- add_map_with_path
- teach coalesce_path() to use add_map_with_path() and verify_paths()
- add a configure() function to the daemon
- teach multipathd to coalesce its map vector after configuration
- multipathd/main.c:reconfigure() restarts the configuration process

Fixed 2 bugs in the implementation from Edward Goggin :

- set mpp wwid before the binded alias lookup so that friendly names
  work
- allocate a mpp->paths in adopt_paths() when mpp->pg is NULL and we
  must store a path there

And fixed one long standing careless bug in all structs.c:find_*().
Being passed a NULL vector shortcuts the lookups now.