Implement aarch64 neon instruction set AdvSIMD (3V Diff), covering the following 26 instructions,

SADDL, UADDL, SADDW, UADDW, SSUBL, USUBL, SSUBW, USUBW, ADDHN, RADDHN, SABAL, UABAL, SUBHN, RSUBHN, SABDL, UABDL, SMLAL, UMLAL, SMLSL, UMLSL, SQDMLAL, SQDMLSL, SMULL, UMULL, SQDMULL, PMULL



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190288 91177308-0d34-0410-b5e6-96231b3b80d8