Move endian utilities to their own file.
diff --git a/source/opcode.cpp b/source/opcode.cpp
index 32fe7fb..fa0159c 100644
--- a/source/opcode.cpp
+++ b/source/opcode.cpp
@@ -25,7 +25,7 @@
 // MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
 
 #include <libspirv/libspirv.h>
-#include "binary.h"
+#include "endian.h"
 #include "instruction.h"
 #include "opcode.h"