patch 9.0.0980: the keyboard state response may end up in a shell command

Problem:    The keyboard state response may end up in a shell command.
Solution:   Only request the keyboard protocol state when the typeahead is
            empty, no more commands are following and not exiting.  Add the
            t_RK termcap entry for this.

src/os_unix.c

@@ -5379,7 +5379,7 @@ finished:
 
 		if (tmode == TMODE_RAW)
 		    // possibly enables modifyOtherKeys again
-		    out_str(T_CTI);
+		    out_str_t_TI();
 	    }
 # endif