Use little-endian order by default for U64 struct

Most Arduino platforms are little-endian. PowerPC, if explicitly specified will use big-endian order.

Author: wxorx

src/libhelix-aac/assembly.h

@@ -558,14 +558,14 @@ static __inline int CLZ(int x)
 typedef union _U64 {
 	Word64 w64;
 	struct {
-#ifdef __XTENSA__		
-		unsigned int lo32;
-		signed int   hi32;
-#else
+#if defined(__POWERPC__) || defined(__powerpc__)
 		/* PowerPC = big endian */
 		signed int   hi32;
 		unsigned int lo32;
-#endif		
+#else
+		unsigned int lo32;
+		signed int   hi32;
+#endif
 	} r;
 } U64;