Adds the evex-promoted opcodes vpunpcklbw, vpunpcklwd, vpunpckldq, vpunpcklqdq, vpunpckhbw, vpunpckhwd, vpunpckhdq, vpunpckhqdq, vpacksswb, vpackssdw, vpackuswb, vpackusdw.
Adds tests for above.
Opcodes have been checked against llvm-mc, binutils/gas/objdump and capstone.
Issue: #1312