Move more of the utility headers into /include/mcaselector-lite.

These headers have no associated C files, and are mainly used for
utility logic.
Having them in `/include` makes them more easily located, and more
globally used.

We are using "classic" header guards here over `#pragma once` for better
support. Since `#pragma once` is defined by the compiler, rather than
standard C.
Why isn't it used across the project? I have no idea.

src/dat/mcx.c

@@ -7,13 +7,13 @@
 
 #include <archive.h>
 #include <assert.h>
-#include <endian.h>
+#include <mcaselector-lite/endian.h>
+#include <mcaselector-lite/types.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
 
-#include "../types.h"
 #include "../util/error.h"
 
 #define SECTOR 0x1000 // sector size