 a "worst case" scenario (input data not compressible)
    This function is primarily useful for memory allocation purposes (destination buffer size).
    Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example).
    Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize)
        inputSize  : max supported value is LZ4_MAX_INPUT_SIZE
        return : maximum output size in a "worst case" scenario
           