unistd does not always include getopt.h (by @velichkov)
diff --git a/skeletons/converter-example.c b/skeletons/converter-example.c
index 854a480..2e7e193 100644
--- a/skeletons/converter-example.c
+++ b/skeletons/converter-example.c
@@ -14,7 +14,7 @@
#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h> /* for atoi(3) */
-#include <unistd.h> /* for getopt(3) */
+#include <getopt.h> /* for getopt(3) */
#include <string.h> /* for strerror(3) */
#include <sysexits.h> /* for EX_* exit codes */
#include <errno.h> /* for errno */