Added backing signatures

src/backing.c

@@ -1,5 +1,7 @@
 #include "backing.h"
 
+#include "entry.h"
+
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
@@ -61,3 +63,4 @@ Result backing_exists(const char* backing_id, bool* out_exists) {
 
 	return SUCCESS;
 }
+