remove unused vis_message_hide() function

the message window gets closed like a normal window and nothing calls
this function. In fact, it wasn't even used when it was added 8 years
ago in 979ab79.

fix use after free in cmd_files()

When the cmd closes the window the window pointer gets freed along the
way. We can't use win->next to update the loop variable if sam_execute()
has been called. Instead we can store win->next early and use that
variable to continue the loop.

fixes #1090

vis-clipboard: make xsel honor --selection

ci: fix authentication by using GITHUB_TOKEN

Fix luadoc to use ~= for status

update test submodule

vis.1: list equivalent key bindings on the same line

it is hard to tell which line <C-u> and <C-d> are supposed to belong to
in the current version.

see #1033

ci: remove deprecated ubuntu-18.04 and switch to ubuntu-latest

ubuntu-latest is supposed to track the newest supported ubuntu release
which as of now is 22.04.

18.04 has been deprecated for a while and seems like it has finally
been removed:

https://github.blog/changelog/2022-08-09-github-actions-the-ubuntu-18-04-actions-runner-image-is-being-deprecated-and-will-be-removed-by-12-1-22/

build: update alpine in docker build to version 3.18

Just a version bump, no changes required.

vis-complete: Fix commandline options handling

check for EOF before unsetting row, col & line cache in view_coord_get

This commit fixes c22b2c2, which introduced a bug when the EOF was
in view.

build: update alpine in docker build to version 3.17

This requires one extra package, as static liblzma (liblzma.a) was
moved to xz-static.

vis: remove unused Arg union member

This was missed when pairwise selection combinators were removed in
404bb95..d1d5853.

don't set _FORTIFY_SOURCE in configure

distributions that want this flag set do so on a system wide level. for
example Gentoo, Fedora, Debian, and OpenSUSE.

since vis sets it when invoking cc via make it overwrites the system
setting (and pollutes the output with redefinition warnings).

For reference here is the related bug in Gentoo:
https://bugs.gentoo.org/892960

fix bug where visual-line selections after view were considered visible

prior to this patch, if you had a visual-line selection after the view,
and try to move it(& all other selections) up into the buffer, the
selection would appear prematurely.

https://github.com/martanne/vis/issues/1074

implement Selection:remove()

lua: Make luacheck happy

update changelog

vis-open: further improvement & clean-up

Do tilde expansion only for the tilde character at the beginning of the pattern.