userspace: Add Generic Segmentation Offloading. #2381

Job	Run time
dpdk gcc	5s
linux rpm fedora	4m 36s
osx clang --disable-ssl	3m 6s
linux deb no dpdk	6m 33s
linux gcc --disable-ssl	2m 10s
linux clang --disable-ssl	2m 7s
linux gcc c99	2m 11s
linux clang c99	2m 4s
linux gcc test	6m 29s
linux clang test asan	10m 45s
linux clang test ubsan	7m 21s
linux gcc test --enable-shared	8m 48s
linux clang test --enable-shared	8m 39s
linux gcc check check-dpdk dpdk	13m 54s
linux clang check check-dpdk dpdk	13m 32s
linux gcc test -ljemalloc	6m 51s
linux clang test -ljemalloc	6m 49s
linux gcc --enable-afxdp	2m 5s
linux clang --enable-afxdp	2m 12s
linux gcc dpdk --enable-shared	3m 6s
linux clang dpdk --enable-shared	2m 52s
linux gcc dpdk-shared	2m 20s
linux clang dpdk-shared	2m 14s
linux gcc dpdk-shared --enable-shared	2m 59s
linux clang dpdk-shared --enable-shared	2m 51s
linux gcc m32 --disable-ssl	2m 9s
	2h 8m 48s

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