Adding missing headers.

Author: syzdek

src/securecoreutils.c

@@ -50,6 +50,7 @@
 #include <errno.h>
 #include <sys/stat.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "widget-cat.h"
 #include "widget-pathcheck.h"