The new oldtest directory is in test/old/testdir. The reason for this is
that many tests have hardcoded the parent directory name to be
'testdir'.

Problem:    Small inconsitency in highlight test.
Solution:   Use one argument for :execute. (Antony Scriven, vim/vim#6975)

https://github.com/vim/vim/commit/2bbada811625ee53c7bcdf689dbf409e9975ea8f

Problem:    Tests use hand coded feature and option checks.
Solution:   Use the commands from check.vim in more tests.

https://github.com/vim/vim/commit/8c5a278fc508da6dfe50e69b6ee734451aa4eafb

Omit Test_wincolor(): there are later patches that touch that function.
Omit test_memory_usage.vim: a Lua test is used for that file.
Cherry-pick Test_issue_3969() from patch 8.1.0969.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    The Athena GUI support is outdated.
Solution:   Remove the Athena GUI code.
https://github.com/vim/vim/commit/0b962e5685edd41b55d5427b894797e725707639

Problem:    Several errors are not tested for.
Solution:   Add tests. (Yegappan Lakshmanan, closes vim/vim#5892)
https://github.com/vim/vim/commit/ee4e0c1e9a81cb5d96e0060203a9033c2f28588e

Omit Test_range() change: reverted in patch 8.2.0615.
Cherry-pick Test_z_no_space_before_xxx() from patch 8.2.0195.
Cherry-pick Test_reverse_sort_uniq() change from patch 8.2.0183.
Make uniq() error behavior consistent with sort().
Cherry-pick Test_set_ttytype() change from patch 8.1.1826.
Cherry-pick quickfix checks from patch 8.1.2373 to test_preview.vim.
Test_viminfo_error() is applicable.
Cherry-pick E1058 from patch 8.2.0149 and port Test_deep_nest() to Lua.

Problem:    Redrawing could be a bit more efficient.
Solution:   Optimize redrawing. (closes vim/vim#10105)
https://github.com/vim/vim/commit/8c9796085071950f9a03ca0fe116608e4f86aac2

Problem:    Cursorcolumn is sometimes not correct.
Solution:   Recompute the cursor column when entering Insert mode and the
            cursor is on a character wider than a screen cell.
https://github.com/vim/vim/commit/782c6744b49b30d9460ed00d4773666e42e07163

Problem:    Superfluous check if a redraw is needed for 'cursorline'.
Solution:   Remove check_redraw_cursorline(). (closes vim/vim#10030, closes vim/vim#10029)
https://github.com/vim/vim/commit/3e559cd88486ffab6b6fb4e0921b4600d137a617

redraw_after_callback() is N/A.
Omits changes that just revert code from patch 8.2.4630.

Ref: #9342

Adds the option to have a single global statusline for the current window at the bottom of the screen instead of a statusline at the bottom of every window. Enabled by setting `laststatus = 3`.

Due to the fact that statuslines at the bottom of windows are removed when global statusline is enabled, horizontal separators are used instead to separate horizontal splits. The horizontal separator character is configurable through the`horiz` item in `'fillchars'`. Separator connector characters are also used to connect the horizontal and vertical separators together, which are also configurable through the `horizup`, `horizdown`, `vertleft`, `vertright` and `verthoriz` items in `fillchars`.

The window separators are highlighted using the `WinSeparator` highlight group, which supersedes `VertSplit` and is linked to `VertSplit` by default in order to maintain backwards compatibility.