Change curses' use of menuitem_invert_test() to match the recently
changed tty behavior: when menuinvertmode is 1 the test excludes
special menu items that are flagged 'skip-invert' while handling
select-all and select-page as well as invert-all and invert-page,
and when that option is 2 then it also operates on deselect-all and
deselect-page.
0cd98c402d