multiplex sysfs hwmon lookup

Seems like sysfs paths have changed for hwmon coretemp/sensors
(as of kernel 3.15/3.16), look for information in both places.

Other changes:
* non-Thinkpads only: report speed of all fans, not just the first one
* eliminate "cat | awk" pipe (IBMFAN)

Signed-off-by: Thomas Koch <linrunner@gmx.net>
changelog.
Consider changed sysfs paths for i915 enable_rc6/fbc as of kernel 3.15 (M@C).