[mod_auth] include unistd.h for crypt() on Mac OS
#elif defined(__linux__)
/* linux needs _XOPEN_SOURCE */
# define _XOPEN_SOURCE
+#elif defined(__APPLE__) && defined(__MACH__)
+#include <unistd.h>
#endif
#if defined(HAVE_LIBCRYPT) && !defined(HAVE_CRYPT)
