Update hwpmc to support Haswell class processors.
0x3C:      /* Per Intel document 325462-045US 01/2013. */

Add manpage to document all the goodness that is available in this
processor model.

Submitted by:	hiren panchasara <hiren.panchasara@gmail.com>
Reviewed by:	jimharris, sbruno
Obtained from:	Yahoo! Inc.
MFC after:	2 weeks