Update to account for default colour change in libcurses.

PR lib/56388

Regen addstr2.chk after fix for the line-hash bug in libcurses.

Now, all t_curses tests successfully pass on all platforms I have tried.

Thanks blymn@ for kind advice!

Update the check files to account for fixes to addstr.c

New tests and updates for corrected behaviour due to fix for PR56224
* Added extra testing to the addstr test to demonstrate bug described
in PR#56224 and validate case when scrolling enabled still

New tests and updates for corrected behaviour due to fix for PR56224
* Added extra testing to the addstr test to demonstrate bug described
in PR#56224 and validate case when scrolling enabled still works.
* Fixed slk test, the slk_init output changed due to corrected wrapping,
slk_restore no longer returns ERR probably due to addwchar no longer
returning ERR when an implicit scroll was attempted when scrolling
disabled. Commented out the slk_wset test, this is now returning ERR
instead of misbehaving, needs investigation.

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