This changes tui_copy_source_line to use ISCNTRL. This lets it work
more nicely with UTF-8 input. Note that this still won't work for
stateful multi-byte encodings; for that much more work would be
required. However, I think this patch does not make gdb any worse in
this scenario.
gdb/ChangeLog
2020-09-27 Tom Tromey <tom@tromey.com>
PR tui/25342:
* tui/tui-winsource.c (tui_copy_source_line): Use ISNCTRL.