[ruby/io-console] Set OPOST when intr is true

To enable implementation-defined output processing, for the
compatibility with readline.  [Bug #16509]

https://bugs.ruby-lang.org/issues/16509

https://github.com/ruby/io-console/commit/8c8b0b6757

ext/io/console/console.c

@@ -190,6 +190,7 @@ set_rawmode(conmode *t, void *arg)
 	if (r->intr) {
 	    t->c_iflag |= BRKINT;
 	    t->c_lflag |= ISIG;
+	    t->c_oflag |= OPOST;
 	}
 #endif
 	(void)r;