ZSTD_copy16
#define COPY16(d,s) do { ZSTD_copy16(d,s); d+=16; s+=16; } while (0)
ZSTD_copy16(op, ip);
ZSTD_copy16(seqStorePtr->lit, literals);
ZSTD_copy16(op, (*litPtr));
ZSTD_copy16(op, (*litPtr));