Set close-on-exec file for file inputs

We don't want to leak descriptors to child PROCESSES (!= threads) such
as the pseudo-CGI interface. The socket wrappers ahve already been doing
that for a while. Unfortunately, there are still many "leaks", through
underlying libraries, opendir(), fopen(), etc. And then, this is not
thread-safe (we leak if another thread calls fork() between open() and
fcntl()). This is a well-known limitation in POSIX anyway.

modules/access/file.c

@@ -349,6 +349,7 @@ static int open_file (access_t *p_access, const char *path)
                         _("VLC could not open the file \"%s\"."), path);
         return -1;
     }
+    fcntl (fd, F_SETFD, fcntl (fd, F_GETFD) | FD_CLOEXEC);
 
 #if defined(HAVE_FCNTL_H)
     /* We'd rather use any available memory for reading ahead

modules/access/mmap.c

@@ -104,6 +104,7 @@ static int Open (vlc_object_t *p_this)
         msg_Warn (p_access, "cannot open %s: %m", path);
         goto error;
     }
+    fcntl (fd, F_SETFD, fcntl (fd, F_GETFD) | FD_CLOEXEC);
 
     /* mmap() is only safe for regular and block special files.
      * For other types, it may be some idiosyncrasic interface (e.g. packet