Add a new option to the blkid program, -l, which will more efficiently search

Add a new option to the blkid program, -l, which will more efficiently search
for a single device.

Add a new function to the blkid library, blkid_probe_all_new().

Optimize blkid_find_dev_with_tag() so that extraneous device validation are
skipped.  (Makes a difference for system with a large number of disks).