use <fcntl.h> and not <sys/fcntl.h>

open/open_append.c

@@ -1,5 +1,5 @@
 #include <unistd.h>
-#include <sys/fcntl.h>
+#include <fcntl.h>
 #include "open.h"
 
 extern int open_append(const char *filename) {

open/open_excl.c

@@ -1,5 +1,5 @@
 #include <unistd.h>
-#include <sys/fcntl.h>
+#include <fcntl.h>
 #include "open.h"
 
 extern int open_excl(const char *filename) {

open/open_read.c

@@ -1,5 +1,5 @@
 #include <unistd.h>
-#include <sys/fcntl.h>
+#include <fcntl.h>
 #include "open.h"
 
 extern int open_read(const char *filename) {

open/open_trunc.c

@@ -1,5 +1,5 @@
 #include <unistd.h>
-#include <sys/fcntl.h>
+#include <fcntl.h>
 #include "open.h"
 
 extern int open_trunc(const char *filename) {

open/open_write.c

@@ -1,5 +1,5 @@
 #include <unistd.h>
-#include <sys/fcntl.h>
+#include <fcntl.h>
 #include "open.h"
 
 extern int open_write(const char *filename) {