Problem:    Cannot read back what setcellwidths() has done.
Solution:   Add getcellwidths(). (Kota Kato, closes vim/vim#11837)

https://github.com/vim/vim/commit/66bb9ae70f7371456ed76518076d2a344f8ab417

Co-authored-by: Kota Kato <github@kat0h.com>

Problem:    getbufline() is inefficient for getting a single line.
Solution:   Add getbufoneline().

https://github.com/vim/vim/commit/ce30ccc06af7f2c03762e5b18dde37b26ea6ec42

Cherry-pick part of usr_41.txt from patch 8.1.1628.

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

Problem:    col() and charcol() only work for the current window.
Solution:   Add an optional winid argument. (Yegappan Lakshmanan,
            closes vim/vim#11466, closes vim/vim#11461)

https://github.com/vim/vim/commit/4c8d2f02b3ce037bbe1d5ee12887e343c6bde88f

Cherry-pick test_functions.vim change from patch 8.2.0633.

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

Problem:    Cannot have expandcmd() give an error message for mistakes.
Solution:   Add an optional argument to give errors. Fix memory leak when
            expanding files fails. (Yegappan Lakshmanan, closes vim/vim#10071)
https://github.com/vim/vim/commit/2b74b6805b5c8c4836b66df5d949f5ff6a77f8c7

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

Problem:    strchars() defaults to counting composing characters.
Solution:   Add strcharlen() which ignores composing characters.

https://github.com/vim/vim/commit/70ce8a1561c5396e4c4381f76a005cbb97646f80

Use docs from latest Vim instead.

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

Problem:    test_fails() does not check the context of the line number.
Solution:   Use another argument to specify the context of the line number.

https://github.com/vim/vim/commit/9bd5d879c2ecfbdbb168b090e12f4b89724a302e

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

Problem:    Vim9: error for list index uses wrong line number.
Solution:   Set source line number. (closes vim/vim#6724)  Add a way to assert the
            line number of the error with assert_fails().

https://github.com/vim/vim/commit/1d634542cf5ebcd1d5d83bd124b3e1d5e7c96c58

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

Problem:    Vim9: return type of readfile() is any.
Solution:   Add readblob() so that readfile() can be expected to always
            return a list of strings. (closes vim/vim#7671)

https://github.com/vim/vim/commit/c423ad77ed763c11ba67729bbf63c1cf0915231f

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

Problem:    Cannot translate messages in a Vim script.
Solution:   Add gettext().  Try it out for a few messages in the options
            window.

https://github.com/vim/vim/commit/0b39c3fd4c5d1c8ebd2efa85fced7df5e17efd3b

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