Add #include <unistd.h> to provide prototype for getopt()

Signed-off-by: Brian Candler <b.candler@pobox.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

examples/auth/crackcheck/crackcheck.c

@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <ctype.h>
 #include <crack.h>
+#include <unistd.h>
 
 void usage(char *command) {
 	char *c, *comm;