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:    Test for srand() fails on MS-Windows.
Solution:   Do not expect the same result a second time.

https://github.com/vim/vim/commit/9dacdb1d56ee0f9272f3fc956a12f15f84ffb205

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

Problem:    Without /dev/urandom srand() seed is too predictable.
Solution:   Use micro seconds and XOR with process ID. (Yasuhiro Matsumoto,
            closes vim/vim#11656)

https://github.com/vim/vim/commit/f0a9c004825ab686270ee57260652cce25e61049

Co-authored-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>

Problem:    assert_fails() checks the last error message.
Solution:   Check the first error, it is more relevant.  Fix all the tests
            that rely on the old behavior.

https://github.com/vim/vim/commit/9b7bf9e98f06ece595fed7a3ff53ecce89797a53

Skip test_listener.vim, test_textprop.vim, test_viminfo.vim.
Skip test_python2.vim: affected line fails and hasn't been ported.
Skip test_python3.vim: affected lines fail and haven't been ported.
Skip CHECK_LIST_MATERIALIZE.

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

Problem:    Crash when using garbagecollect() in between rand().
Solution:   Redesign the rand() and srand() implementation. (Yasuhiro
            Matsumoto, closes vim/vim#5587, closes vim/vim#5588)
https://github.com/vim/vim/commit/4f645c54efe33d7a11e314676e503118761f08a7

Omit test_srand_seed.
Unmacroify SHUFFLE_XOSHIRO128STARSTAR and SPLITMIX32 while we're at it (leave
ROTL alone as it's fairly innocent).

Problem:    No test with wrong argument for rand().
Solution:   Add a test case.
https://github.com/vim/vim/commit/68e9e5f7fccb8038cf0ca5b5d95c85a923152f46

Problem:    rand() does not use the best algorithm.
Solution:   use xoshiro128** instead of xorshift. (Kaito Udagawa,
            closes vim/vim#5279)
https://github.com/vim/vim/commit/f8c1f9200c4b50969a8191a4fe0b0d09edb38979

Problem:    Using time() for srand() is not very random.
Solution:   use /dev/urandom if available
https://github.com/vim/vim/commit/07e4a197953d12902fb97beb48830a5323a52280

Use os_open and os_close.

time_settime is N/A, so some parts of the test are disabled.

There's maybe a very, very, very, very small chance the /dev/urandom test fails,
but it shouldn't matter. :P

Problem:    Random number generator in Vim script is slow.
Solution:   Add rand() and srand(). (Yasuhiro Matsumoto, closes vim/vim#1277)
https://github.com/vim/vim/commit/06b0b4bc27077013e9b4b48fd1d9b33e543ccf99

Add missing method call usage to builtin.txt.
vim_time and test_settime is N/A.
Add a modeline to test_random.vim.
Use typval_T* over listitem_T* vars so we don't need to use TV_LIST_ITEM_TV all
over the place...
Remove NULL list checks (tv_list_len covers this).