Uses clz and bsr instructions for bit counting on ARM64 platforms as well.

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.4.x@1414 632fc199-4ca6-4c93-a231-07263d6284db

ChangeLog.txt

@@ -13,6 +13,9 @@ instead of -1 if componentID was > 0 and subsamp was TJSAMP_GRAY.
 [3] Fixed an issue in tjBufSizeYUV2() wherby it would erroneously return 0
 instead of -1 if width was < 1.
 
+[5] The Huffman encoder now uses clz and bsr instructions for bit counting on
+ARM64 platforms (see 1.4 beta1 [5].)
+
 
 1.3.90 (1.4 beta1)
 ==================

jchuff.c

@@ -37,7 +37,7 @@
  */
 
 /* NOTE: Both GCC and Clang define __GNUC__ */
-#if defined __GNUC__ && defined __arm__
+#if defined __GNUC__ && (defined __arm__ || defined __aarch64__)
 #if !defined __thumb__ || defined __thumb2__
 #define USE_CLZ_INTRINSIC
 #endif