portability: we use termios.h and sys/ioctl.h

Reported by Maarten De Braekeleer.
https://lists.gnu.org/r/bison-patches/2020-07/msg00079.html

* bootstrap.conf (gnulib_modules): Add termios and sys_ioctl.

src/flex-scanner.h

@@ -121,6 +121,6 @@ static struct obstack obstack_for_string;
     obstack_free (&obstack_for_string, last_string);     \
     last_string = NULL;                                  \
   } while (0)
-#endif
+# endif
 
 #endif