kernel - Add workaround for errata #721 on AMD cpus (found by Matt Dillon)
* Official reference for errata 721:
http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf
* This is the cpu bug found by Matthew Dillon, present on all K10 cores
(so far). AMD has indicated that the bug is not present on Bulldozer
cpus.
* The MSR workaround is now reported and programmed during kernel boot.
* No discernable difference in performance was detected running GCC
with and without the MSR adjustment.
* Verified to have fixed our test case w/GCC. It no longer seg-faults.