Add `SetSockOpt` definitions related to Linux Kernel TLS. #578

Job	Run time
rust_stable	1m 8s
macos	2m 15s
linux_native_builds (x86_64-unknown-linux-gnu)	1m 24s
minver	19s
linux_native_builds (x86_64-unknown-linux-musl)	1m 12s
rustfmt	14s
tier3 (x86_64-unknown-dragonfly)	56s
tier3 (x86_64-unknown-openbsd)	58s
tier3 (x86_64-unknown-haiku)	58s
tier3 (i686-unknown-hurd-gnu)	1m 1s
cross_compiling (aarch64-linux-android)	39s
redox	39s
cross (arm-unknown-linux-gnueabi)	1m 43s
cross_compiling (arm-linux-androideabi)	33s
cross (armv7-unknown-linux-gnueabihf)	1m 42s
cross_compiling (armv7-linux-androideabi)	32s
cross (i686-unknown-linux-gnu)	1m 42s
cross_compiling (i686-linux-android)	39s
cross (i686-unknown-linux-musl)	1m 47s
cross_compiling (x86_64-linux-android)	39s
cross (mips-unknown-linux-gnu)	1m 49s
cross_compiling (arm-unknown-linux-musleabi)	39s
cross (mips64-unknown-linux-gnuabi64)	1m 46s
cross_compiling (x86_64-unknown-fuchsia)	30s
cross (mips64el-unknown-linux-gnuabi64)	1m 49s
cross_compiling (x86_64-unknown-illumos)	30s
cross (mipsel-unknown-linux-gnu)	1m 47s
cross_compiling (aarch64-apple-ios, true)	30s
cross (powerpc64le-unknown-linux-gnu)	1m 49s
cross_compiling (powerpc64-unknown-linux-gnu)	39s
cross_compiling (s390x-unknown-linux-gnu)	38s
cross_compiling (x86_64-unknown-linux-gnux32)	38s
cross_compiling (x86_64-unknown-netbsd)	29s
	34m 33s

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