Use 64-bit holding buffer on Win64 for increased performance


git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@177 632fc199-4ca6-4c93-a231-07263d6284db
diff --git a/jdhuff.h b/jdhuff.h
index b192e48..0a242c5 100644
--- a/jdhuff.h
+++ b/jdhuff.h
@@ -73,7 +73,7 @@
  * necessary.
  */
 
-#if __WORDSIZE == 64
+#if __WORDSIZE == 64 || defined(_WIN64)
 
 typedef size_t bit_buf_type;	/* type of bit-extraction buffer */
 #define BIT_BUF_SIZE  64		/* size of buffer in bits */