First pass at fixing tar segfault, and more portability updates.

-Erik

shell/cmdedit.c

@@ -70,6 +70,12 @@ static struct history *his_end = NULL;	/* Last element in command line list */
 
 /* Current termio and the previous termio before starting sh */
 struct termios initial_settings, new_settings;
+
+
+#ifndef	_POSIX_VDISABLE
+#define	_POSIX_VDISABLE	'\0'
+#endif
+
 #endif