Add support for setting clipboard using OSC 52 escape sequence

[unxed]

Useful if X11 is not available.

OSC 52 support table:
https://github.com/ojroques/vim-oscyank#vim-oscyank

[magiblot]

Hi Unxed! Thanks for the patch. Don't you think it would be better to first try accessing the X11 clipboard before using the OSC 52 escape sequence? This can be detected by checking whether clipboard_set_text_ex failed.

[unxed]

first try accessing the X11 clipboard before using the OSC 52 escape sequence

done!

[unxed]

Maybe the same code should be added to tvision internal editor control also

[magiblot]

I have added a few changes to your initial patch:

• We cannot assume that stdout points to the terminal.
• We cannot assume that text.data() is null-terminated.
• This application is never built with Borland C++.