ncurses: vendor import version 6.5

ncurses: import version 6.2-20210220

Update to 6.2-20200215

While I didn't plan another upgrade, This version incorporate fixes from
kevans@ so let's upgrade to it

Update ncurses to 20200118

Among the changes from before:
- Add support for extended colors on widechar version
- Enable ncurses extended functions
- Enable version 2 of the extended mouse support
-

Update ncurses to 20200118

Among the changes from before:
- Add support for extended colors on widechar version
- Enable ncurses extended functions
- Enable version 2 of the extended mouse support
- Enable SCREEN extensions

Modification that differs from upstream:
- _nc_delink_entries used to be exposed and was turn static,
turn it back as dynamic to not break abi
- Adapt our old termcap.c to modern ncurses

MFC after: 3 weeks

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MFV r262617: ncurses 5.9.

Import ncurses 5.6-20061217 onto the vender branch

Approved by: delphij

Import ncurses-5.2-20020518 onto the vendor branch.

Obtained from: ftp://dickey.his.com/ncurses/

Import the most recent ncurses 5.1 prerelease (20000701).
Mostly this is intended to resolve the trace() badness once and for all.

Obtained from: ftp://dickey.his.com/ncurses/

Import unmodified (but trimmed) ncurses 5.0 prerelease 990821.
This contains the full eti (panel, form, menu) extensions.
bmake glue to follow.

Obtained from: ftp://ftp.clark.net/pub/dickey/ncurses