patch 9.1.0183: Wrong display or screenpos() result when toggling diff mode

Problem:  Wrong display or screenpos() result when toggling diff mode.
Solution: Reset w_skipcol when disabling 'wrap'.  Reset w_leftcol when
          enabling 'wrap' (zeertzjq).

fixes: #14210
closes: #14211

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index b44879f..7602bd3 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ