Problem:    curpos() does not accept a string argument as before.
solution:   Make a string argument work again. (Yegappan Lakshmanan,
            closes #7690

Problem:    "char" functions return the wront column in Insert mode when the
            cursor is beyond the end of the line.
Solution:   Compute the column correctly. (Yegappan Lakshmanan, closes #7669)

Problem:    Not easy to get mark en cursor posotion by character count.
Solution:   Add functions that use character index. (Yegappan Lakshmanan,
            closes #7648)

Problem:    Vim9: no error when using "2" for a line number.
Solution:   Give an error message if the line number is invalid. (closes #7492)

Problem:    screenpos() does not include the WinBar offset.
Solution:   Use W_WINROW() instead of directly using w_window. (closes #7487)

Problem:    Not enough testing for movement commands.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #6313)

Problem:    Crash with null partial and blob.
Solution:   Check for NULL pointer.  Add more tests. (Yegappan Lakshmanan,
            closes #5984)

Problem:    Some tests are still old style.
Solution:   Convert to new style tests. (Yegappan Lakshmanan, closes #5957)

Problem:    screenpos() returns wrong values when 'number' is set. (Ben
            Jackson)
Solution:   Compare the column with the window width. (closes #5133)

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.