blkid: Add support for probing exFAT

 * e2fsprogs can't currently detect exFAT filesystems.
 * Apply patch from GoogleTV to add support.

Change-Id: Ib08bdb1d13e995d133a62539e3bfa0e3a22eeead
Merge "blkid: Add support for probing exFAT" into jb-mr1

Change-Id: I66d7490b153b6147be614aab743c063ef9a90a8c