dup3's behavior differs from dup2 in this case, so we need to paper over that in the C library. Change-Id: I313cd6f226db5e237f61866f324c5ecdd12bf762
(aarch64 kernels only have the newer system calls.) Also expose the new functionality that's exposed by glibc in our header files. Change-Id: I45d2d168a03f88723d1f7fbf634701006a4843c5