patch 9.2.0262: invalid lnum when pasting text copied blockwise

patch 9.2.0262: invalid lnum when pasting text copied blockwise

Problem:  invalid lnum when pasting text copied blockwise
          (KillTheMule)
Solution: Subtract nr_lines from curwin->w_cursor.lnum when calling
          changed_lines() in do_put() (Pierluigi Lenoci)

When doing a blockwise paste beyond the end of the buffer, new lines are
appended and nr_lines is incremented accordingly. However, the
changed_lines() call used curwin->w_cursor.lnum as the "lnume" argument
(the first line below the changed lines BEFORE the change), which is
incorrect because the cursor has already been moved past the newly
appended lines.

Fix by subtracting nr_lines from curwin->w_cursor.lnum, so that lnume
correctly reflects the state before the change, as documented in
changed_lines().

Add a listener test to verify the correct values are reported.

Port of neovim/neovim#12733.

fixes:  #6660
closes: #19844

Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>