Move fcntl.h to internal defines and check for O_CLOEXEC.

lib/verity/verity.c

@@ -25,7 +25,6 @@
 #include <stdint.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <fcntl.h>
 #include <netinet/in.h>
 #include <uuid/uuid.h>
 

lib/verity/verity_fec.c

@@ -20,7 +20,6 @@
  */
 
 #include <stdlib.h>
-#include <fcntl.h>
 #include <errno.h>
 
 #include "verity.h"