Add a nasty temporary kludge to CPUID that allows 64-bit MacOSX 10.10
(Yosemite) to run, until such time as XSAVE and XRSTOR are implemented.
Detailed in the comments.  All other targets should be unaffected.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2989 8f6e269a-dfd6-0310-a8e1-e2731360e62c