Restore previously discarded (and incomplete) OS9 backend files.

src/os9.h

@@ -0,0 +1,10 @@
+/*  $Revision: 1.1 $
+**
+**  Editline system header file for OS-9 (on 68k).
+*/
+
+#define CRLF		"\r\l"
+#define FORWARD		extern
+
+#include <dir.h>
+typedef struct direct	DIRENTRY;