updated ZSTD_estimate?DictSize() to pass parameter byReference

resulting ?Dict object is smaller when created byReference.
Seems better than a documentation note.

lib/decompress/zstd_decompress.c

@@ -2053,10 +2053,10 @@ size_t ZSTD_freeDDict(ZSTD_DDict* ddict)
 
 /*! ZSTD_estimateDDictSize() :
  *  Estimate amount of memory that will be needed to create a dictionary for decompression.
- *  Note : if dictionary is created "byReference", reduce this amount by dictSize */
-size_t ZSTD_estimateDDictSize(size_t dictSize)
+ *  Note : dictionary created "byReference" are smaller */
+size_t ZSTD_estimateDDictSize(size_t dictSize, unsigned byReference)
 {
-    return dictSize + sizeof(ZSTD_DDict);
+    return sizeof(ZSTD_DDict) + (byReference ? 0 : dictSize);
 }
 
 size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict)