Update hwpmc to support core events for Atom Silvermont microarchitecture.
(Model 0x4D as per Intel document 330061-001 01/2014)

Tested by:	Olivier Cochard-Labbe <olivier@cochatrd.me>
MFC after:	4 weeks
ext2fs: minor update to the dirpref policy.

Bring in a minor change to the dirpref policy based on r248623.

This is pretty minimal change to keep the implementation in
sync with UFS but other parts from the original change are not
directly applicable so don't expect improvements in fsck times.

MFC after:	2 weeks