Changed ZSTD_compressBound()
Changed ZSTD_compressBound()

required so that if Total = A+B
compressBound(Total) <= compressBound(A) + compressBound(B)
under condition of a minimum size for A and B

Will help for ZSTDMT_compress() memory allocation

Cyan4973/zstd,Cyan4973/zstd,Cyan4973/zstd,Majlen/zstd,Majlen/zstd,Majlen/zstd,Majlen/zstd,Cyan4973/zstd,Cyan4973/zstd