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:    New behavior of b:changedtick not tested.
Solution:   Add a few test cases. (Daniel Hahler)
https://github.com/vim/vim/commit/260addf7955f3695d3daef9dcf840952af9fd851

vim-patch:8.0.0334
vim-patch:8.0.0335
vim-patch:8.0.0343
vim-patch:8.0.0345

Problem:    Can't access b:changedtick from a dict reference.
Solution:   Make changedtick a member of the b: dict. (inspired by neovim
            vim/vim#6112)
https://github.com/vim/vim/commit/79518e2ace5fce7b9c49060e462a6e935dba0a84

vim-patch:8.0.0343: b:changedtick can be unlocked
Problem:    b:changedtick can be unlocked, even though it has no effect.
            (Nikolai Pavlov)
Solution:   Add a check and error E940. (closes #1496)

vim-patch:8.0.0345: islocked('d.changedtick') does not work
Problem:    islocked('d.changedtick') does not work.
Solution:   Make it work.

vim-patch:8.0.0335: functions test fails
Problem:    Functions test fails.
Solution:   Use the right buffer number.
https://github.com/vim/vim/commit/507647da3151f7ffccac1b217936240daa79849c