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:    Quickfix listing does not handle very long messages.
Solution:   Use a growarray instead of a fixed size buffer. (Yegappan
            Lakshmanan, closes vim/vim#11357)

https://github.com/vim/vim/commit/f8412c9d7cc487dacf47a217ae947da68a525c53

Override Test_very_long_error_line() with a rewrite that doesn't use
deferred delete and string interpolation.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

vim-patch:8.2.3564: invalid memory access when scrolling without valid screen

Problem:    Invalid memory access when scrolling without a valid screen.
Solution:   Do not set VALID_BOTLINE in w_valid.

https://github.com/vim/vim/commit/777e7c21b7627be80961848ac560cb0a9978ff43

Remove -Z flag when using RunVim().

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

Problem:    Test 49 is old style.
Solution:   Convert remaining parts to new style. Remove obsolete items.
            (Yegappan Lakshmanan, closes vim/vim#6683)

https://github.com/vim/vim/commit/f7c4d83609acdfe0e4d0fec9413697ac97c0c3f9

Problem:    Crash when no errors and 'quickfixtextfunc' is set.
Solution:   Do not handle errors if there aren't any.

https://github.com/vim/vim/commit/4f1b083be43f351bc107541e7b0c9655a5d2c0bb

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

Problem:    Callback name argument is changed by setqflist().
Solution:   Use the expanded function name for the callback, do not store it
            in the argument. (closes vim/vim#11653)

https://github.com/vim/vim/commit/c96b7f5d2af241c5eb1589e9da3dc09e45355e65

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

Problem:    Filetype autocmd may cause freed memory access.
Solution:   Set the quickfix-busy flag while filling the buffer.

https://github.com/vim/vim/commit/d0fab10ed2a86698937e3c3fed2f10bd9bb5e731

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

Problem:    Cannot use script-local function for setting *func options.
Solution:   Use the script context. (Yegappan Lakshmanan, closes vim/vim#9362)

https://github.com/vim/vim/commit/db1a410b610b2c1941311acc57dcc4afec20720e

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    Function name does not match autocmd event name.
Solution:   Rename "optionsset" to "optionset". (closes vim/vim#11630)

https://github.com/vim/vim/commit/269aa2b29ac3e4c0083d929e2477c95e7bd1177a