[$] A possible end to the FSGSBASE saga

The FSGSBASEpatch series is up to its thirteenth version as of late May. Itenables some "new" instructions for the x86 architecture, opening the way for a number ofsignificant performance improvements. One might think that such a patchseries would be a shoo-in, but FSGSBASE has had a troubled history;meanwhile, the delays in getting it merged may have led to a number ofusers installing root holes on their Linux systems in the hope of improvingsecurity.