Fix include for Win32

src/syncterm/st_crypt.c

 /* Copyright (C), 2007 by Stephen Hurd */
 
 #include <stdio.h>	/* NULL */
-#include <unistd.h>	/* _exit() */
+#ifdef _WIN32
+	#include <stdlib.h>
+#else
+	#include <unistd.h>	/* _exit() */
+#endif
 #include "st_crypt.h"
 #include <xp_dl.h>