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:    Insufficient testing for invalid function arguments.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5988)

https://github.com/vim/vim/commit/99fa721944dda9d07c53c907c33466728df5c271

Omit test_listener.vim: changed again in patch 8.2.1183.
Omit test_textprop.vim: changed again in patch 8.2.1183.
Cherry-pick quickfix feature checks from patch 8.1.2373.
Omit Test_saveas() change: duplicate and removed in patch 8.2.0866.

This is a port of these two patches combined:

vim-patch:8.1.1524: tests are silently skipped

Problem:    Tests are silently skipped.
Solution:   Throw an exception for skipped tests in more places.
https://github.com/vim/vim/commit/b0f94c1ff34d27d33aa9f96204985ea29c2eb0a1

vim-patch:8.1.1544: some balloon tests don't run when they can

Problem:    Some balloon tests don't run when they can.
Solution:   Split GUI balloon tests off into a separate file. (Ozaki Kiichi,
            closes vim/vim#4538)  Change the feature check into a command for
            consistency.
https://github.com/vim/vim/commit/b46fecd3454399f8ebdc5055302e4bfc5a10f98b

Omit test_lua.vim: previous patches are N/A
Omit test_memory_usage.vim: previous patches are N/A
Omit test_textprop.vim: previous patches are N/A
Omit test_winbar.vim: previous patches are N/A
Omit test_termcodes.vim: mostly N/A
Skip Test_mouse_positon() because it uses test_setmouse().
Cannot throw error in a Test_nocatch_ test.
Use latest `CheckFeature clipboard_working` for test_quotestar.vim

Cannot be fully ported as the remote_*() functions from +clientserver
are not yet ported. Include the test changes anyway.

line()'s optional winid argument was already ported. (Wasn't added in
this patch; this just adds documentation)

Add missing test file.
https://github.com/vim/vim/commit/cb00f039332d3188931035e9d07144546fdea78a