Instead of nested linked lists, store autocommands in a flat, contiguous
kvec_t, with one kvec_t per event type. Previously patterns were stored
in each node of the outer linked list, so they can be matched only once
on repeating patterns. They are now reference counted and referenced in
each autocommand, and matching is skipped if the pattern repeats. Speeds
up creation and deletion, execution is not affected.

Co-authored-by: ii14 <ii14@users.noreply.github.com>

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:    Regexp benchmark stest is old style.
Solution:   Make it a new style test.  Fix using a NULL list.  Add more tests.
            (Yegappan Lakshmanan, closes vim/vim#5963)

https://github.com/vim/vim/commit/ad48e6c1590842ab6d48e6caba3e9250734dae27

N/A patches:
vim-patch:9.0.0829: wrong counts in macro comment

Problem:    Regexp and other code not tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5904)

https://github.com/vim/vim/commit/004a6781b3cf15ca5dd632c38cc09bb3b253d1f8

add benchmark from #18109

https://github.com/mpeterv/luacheck/pull/81#issuecomment-261099606

> If you really want to use bleeding-edge version you should get the
> rockspec from master branch, not a fixed commit ...
> The correct way to install from a specific commit is cloning that
> commit and running "luarocks make" from project directory. The reason
> is that running "install" or "build" on an scm rockspec fetches
> sources from master but uses build description from the rockspec
> itself, which may be outdated.

Vim creates these scripts in test1 depending on what build features
are enabled so that tests that use these features are skiped if
necessary. Because Neovim only has one type of build (and the features
+eval, +windows, and +multi-byte are enabled in this build) they are
not necessary.