Fix md5cmp on AmigaOS 4 (PowerPC big-endian)

+ Document AmigaOS support in the change log.

Based on:
chris-y@b4f3b75

Closes libjpeg-turbo#119

ChangeLog.md

@@ -13,6 +13,9 @@ code in libjpeg-turbo from building.
 version of TJBench from outputting any reference images (the `-nowrite` switch
 was accidentally enabled by default.)
 
+4. libjpeg-turbo should now build and run on AmigaOS 4 (with full AltiVec
+SIMD acceleration.)
+
 
 1.5.1
 =====

md5/md5.c

@@ -31,6 +31,15 @@
 
 #include "./md5.h"
 
+#ifdef __amigaos4__
+#include <machine/endian.h>
+#define le32toh(x) (((x & 0xff) << 24) | \
+                    ((x & 0xff00) << 8) | \
+                    ((x & 0xff0000) >> 8) | \
+                    ((x & 0xff000000) >> 24))
+#define htole32(x) le32toh(x)
+#endif
+
 static void MD5Transform(unsigned int [4], const unsigned char [64]);
 
 #if (BYTE_ORDER == LITTLE_ENDIAN)