fixed zbufftest

preserve "pledgedSrcSize=0" means "unknown" in init_advanced()

lib/deprecated/zbuff_compress.c

@@ -72,6 +72,7 @@ size_t ZBUFF_compressInit_advanced(ZBUFF_CCtx* zbc,
                                    const void* dict, size_t dictSize,
                                    ZSTD_parameters params, unsigned long long pledgedSrcSize)
 {
+    if (pledgedSrcSize==0) pledgedSrcSize = ZSTD_CONTENTSIZE_UNKNOWN;  /* preserve "0 == unknown" behavior */
     return ZSTD_initCStream_advanced(zbc, dict, dictSize, params, pledgedSrcSize);
 }