Proposed ncursesw changes for fixing python311

[Jonathan Perkin <jperkin%mnx.io@localhost>]

FWIW these are the changes I am currently testing:

  https://github.com/NetBSD/pkgsrc/compare/ede2764be2b5d6bd3f2e1b8a52efe0ab3d2b1880...TritonDataCenter:pkgsrc:bulktest/upstream-trunk

I'm currently building them against a revision from a couple of weeks 
ago when the tree was a lot more stable first, and then will test 
against an updated tree with the python311 fix applied.  It is able to 
build all of the previous lang/python* packages at least.

Effectively what this does is:

 - if a package depends on ncursesw

 - do NOT buildlink3 ncurses as well like previously

 - instead, create ncurses -> ncursesw symlink in .buildlink/include for 
   compatibility with apps that hardcode #include <ncurses/*.h>

This should avoid issues where ncursesw is required but things end up 
using the ncurses headers, as well as simplifying things (a good thing, 
given how complex this all is).

I'm not confident this won't break other OS, so help testing would be 
appreciated, especially where USE_BUILTIN.ncursesw=yes as I don't have 
any of those readily available at the moment.

--
Jonathan Perkin   -   mnx.io   -   pkgsrc.smartos.org
Open Source Complete Cloud   www.tritondatacenter.com