[$] Much ado about SBAT

Sometimes, the shortest patches lead to the longest threads; for a case inpoint, see thisthree-line change posted by Emanuele Giuseppe Esposito. The purpose ofthis change is to improve the security of locked-down systems by adding a"revocation number" to the kernel image. But, as the discussion revealed,both the cost and the value of this feature are seen differently across thekernel-development community.