Fix 197259  Unsupported arch_prtctl PR_SET_GS option
(valgrind side).
In summary: we were counting somewhat on the luck for FS,
we now similarly count on luch for GS
See VEX commit log r3043 for more details.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14815 a5019735-40e9-0310-863c-91ae7b9d1cf9