Several changes to udev support code:

Several changes to udev support code:

 - we have these levels when the udev rules are processed:
   10-dm.rules --> [11-dm-<subsystem>.rules] --> [12-dm-permissions.rules] -->
   13-dm-disk.rules --> [...all the other foreign rules...] --> 95-dm-notify.rules

 - each level can be disabled now by
   DM_UDEV_DISABLE_{DM, SUBSYSTEM, DISK, OTHER}_RULES_FLAG

 - add DM_UDEV_DISABLE_DM_RULES_FLAG to disable 10-dm.rules

 - add DM_UDEV_DISABLE_OTHER_RULES_FLAG to disable all the other (non-dm) rules.
   We cutoff these rules by using the 'last_rule', so this one should really be
   used with great care and in well-founded situations. We use this for lvm's
   hidden and layer devices now.

 - add a parameter for add_dev_node, rm_dev_node and rename_dev_node so it's
   possible to switch on/off udev checks

 - use DM_UDEV_DISABLE_DM_RULES_FLAG and DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG
   if there's no cookie set and we have resume, remove and rename ioctl.
   This could happen when someone uses the libdevmapper that is compiled with
   udev_sync but the software does not make use of it. This way we can switch
   off the rules and fallback to libdevmapper node creation so there's no
   udev/libdevmapper race.