Add byte order swapping macros to configure

Changes:

    * Make ./configure generate src/config.h, which will contain the
      appropriate #include for endian.h, or #defines to provide
      alternatives

    * Make sure to include config.h in src/frame.c to allow compiling
      on macOS

configure

@@ -17,11 +17,22 @@ create_darwin_config_h() {
     cat <<EOF > src/config.h
 #ifndef _CONFIG_H
 #define _CONFIG_H
-#include <architecture/byte_order.h>
+#include <libkern/OSByteOrder.h>
 
-#ifdef __LITTLE_ENDIAN__
-#define __DO_SWAP_BYTES
-#endif /* _DO_SWAP_BYTES */
+#define htobe16(n) OSSwapHostToBigInt16(n)
+#define htole16(n) OSSwapHostToLittleInt16(n)
+#define be16toh(n) OSSwapBigToHostInt16(n)
+#define le16toh(n) OSSwapLittleToHostInt16(n)
+
+#define htobe32(n) OSSwapHostToBigInt32(n)
+#define htole32(n) OSSwapHostToLittleInt32(n)
+#define be32toh(n) OSSwapBigToHostInt32(n)
+#define le32toh(n) OSSwapLittleToHostInt32(n)
+
+#define htobe64(n) OSSwapHostToBigInt64(n)
+#define htole64(n) OSSwapHostToLittleInt64(n)
+#define be64toh(n) OSSwapBigToHostInt64(n)
+#define le64toh(n) OSSwapLittleToHostInt64(n)
 #endif /* _CONFIG_H */
 EOF
 }

src/frame.c

@@ -3,6 +3,7 @@
 #include <errno.h>
 
 #include <patty/ax25.h>
+#include "config.h"
 
 static ssize_t decode_station(patty_ax25_addr *addr,
                               void *data,