Several changes in dmsetup and libdevmapper:

Several changes in dmsetup and libdevmapper:

 - add DM_UDEV_DISABLE_LIBRARY_FALLBACK udev flag to rely on udev only

 - export dm_udev_create_cookie function to create new cookies on demand

 - add --udevcookie, udevcreatecookie and udevreleasecookie for dmsetup
   (to support "udev transactions" where one cookie value can be used for
    several dmsetup calls)

 - don't use DM_UDEV_DISABLE_CHECKING env. var. anymore and set the state
   automatically (based on udev and libdevmapper dev path comparison)