Basic perf PMU support for Haswell v8

This is based on v7 of the full Haswell PMU support, but 
ported to the latest perf/core and stripped down to the
bare bones

Only for very extremly basic usage.

Most interesting new features are not in this patchkit
(full version is git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git hsw/pmu5)

Contains support for:
- Basic Haswell PMU and PEBS support
- Late unmasking of the PMI
- Support for wide counters

v2: Addressed Stephane's feedback. See individual patches for details.
v3: now even more bite-sized. Qualifier constraints merged earlier.
v4: Rename some variables, add some comments and other minor changes.
Add some Reviewed/Tested-bys.
v5: Address some minor review feedback. Port to latest perf/core
v6: Add just some variable names, add comments, edit descriptions, some
more testing, rebased to latest perf/core
v7: Expand comment
v8: Rename structure field.

-Andi